check engine light o2

need some info

auto4x4 said:

sorry about incomplete wording or what ever. thinking faster than i can type. Tuesday night i pulled a code 1131. the check engine light was already out. Drove the car, to and from work on Wednesday. Eighteen miles round trip, car drove ok. Drove it Thursday, ran good on the way in, was going to swap O2's. As suggested earlier, put the car on the lift, and decide to rescan, didn't write down codes. No 1131, how ever theft mobolizer was active and obd 2 readiness not complete. Also scanner showed 600+ misfires but no codes for misfire,found on net, the same problem, swapped O2's and still had the same problem/1131. Find today possible wiring harness issue, saying short or bad connection in harness. But now the other issue is trans shifting , no codes, but does down shift very hard. Asking any possible ecm problems, one code, harness issue and shifting problem. Are any of the three connected. No other problems, this is what the car has been doing and what the codes have come up on scanner.

Click to expand...

I can send you alot on this but if only if you still need it,,,,,po 1131 is easy..bad wire or o2 is my guess thier,,,,,,,right front ,,,,,,the other im confused on your discription ....600 + misfires????????? What type of scanner are you using????????

clean the MAF?

post 1

2003 PCED OBD SECTION 1: Description and Operation
Procedure revision date: 08/28/2003

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Heated Oxygen Sensor (HO2S) Monitor
The HO2S Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration which can affect emissions. The fuel control or Stream 1 HO2S sensors are checked for proper output voltage and response rate (the time it takes to switch from lean to rich or rich to lean). Stream 2 HO2S sensors used for Catalyst Monitoring, and Stream 3 HO2S sensors used for FAOS (Fore-Aft Oxygen Sensor) control are also monitored for proper output voltage. Input is required from the ECT or CHT, IAT, MAF and CKP sensors to activate the HO2S Monitor. The Fuel System Monitor and Misfire Detection Monitor must also have completed successfully before the HO2S Monitor is enabled.

The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt. The HO2S Monitor evaluates the Stream 1 (Fuel Control) and Stream 2 (Catalyst Monitor) and the Stream 3 (FAOS Control) HO2Ss for proper function.
Once the HO2S Monitor is enabled, the Stream 1 HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage. A fixed frequency closed loop fuel control routine is executed and the Stream 1 HO2S voltage amplitude and output response frequency are observed. A sample of the Stream 1 HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate. A HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the Output State Monitor (OSM) and by measuring the current going through the heater circuit. Since the 2002 Model Year, vehicles will monitor the HO2S signal for a high voltage, in excess of 1.5 volts. The HO2S Monitor DTCs can be categorized as follows:
The MIL is activated after a fault is detected on two consecutive drive cycles.
The HO2S Monitor DTCs can be catagorized as follows:

HO2S signal circuit malfunction - P0131, P0136, P0151, P0156.
HO2S slow response rate - P0133, P0153.
HO2S circuit high voltage - P0132, P0138, P0144, P0152, P0158, P0164.
HO2S heater circuit malfunction - P0135, P0141, P0155, P0161, P0147, P0167.
HO2S heater current malfunction - P0053, P0054, P0055, P0059, P0060, P0061.
Donwstream HO2S not running in on-demand self test - P1127.
Swapped HO2S connectors - P0040, P0041, P1128, P1129, P2278.
HO2S lack of switching - P1131, P1132, P1151, P1152, P2195, P2196, P2197, P2198.
HO2S lack of switching (Sensor indicates lean) - P1137, P1157, P2270, P2272, P2274, P2276.
HO2S lack of switching (Sensor indicates rich) - P1138, P1158, P2271, P2273, P2275, P2277.





Figure 11: Heated Oxygen Sensor Monitor




Figure 12: Heated Oxygen Sensor Monitor - PZEV (Partial Zero Emission Vehicle) Focus Only



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post 2

2003 PCED OBD SECTION 1: Description and Operation
Procedure revision date: 08/28/2003

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Powertrain Control Software

Multiplexing
The increased number of modules on the vehicle necessitates a more efficient method of communication. Multiplexing is a method of designating a system for sending two or more signals simultaneously over a single circuit. In an automotive application, multiplexing is used to allow two or more electronic modules to communicate simultaneously over a single media. Typically this media is a twisted pair of wires. The information or messages that can be communicated on these wires consists of commands, status or data. The advantage of using multiplexing is to reduce the weight of the vehicle by reducing the number of redundant components and electrical wiring.


Multiplexing Implementation
Currently Ford Motor Company uses two different types of communication language protocols to communicate with the powertrain control module (PCM). These protocols are Standard Corporate Protocol (SCP) and Controller Area Network (CAN). Starting with the 2003 model year, Ford will phase-in High Speed-CAN (HS-CAN) for PCM communication with the following vehicles:

LS6
LS8
Thunderbird
2.3L Focus PZEV (partial zero emission vehicle)
The LS and Thunderbird will use HS-CAN between the DCL (Data Communication Link) connector and the PCM for scan tool to PCM diagnostics only. Inter communication (PCM to other network modules) for the LS and Thunderbird will continue to use SCP. The 2.3L Focus PZEV will use HS-CAN for PCM and instrument cluster (IC) module communication and for scan tool diagnostics.

All other vehicles for model year 2003 will continue to use SCP as its communication media for the PCM.


Standard Corporate Protocol (SCP)
SCP is a communication language protocol based on SAE J1850 and is used by Ford Motor Company for exchanging bi-directional message (signals) between electronic modules. Two or more signals can be sent over one SCP network circuit. Fords SCP network operates at 41.6kB/sec (kilobytes per second).

Included in these messages is diagnostic data that is outputted over the BUS (+) and BUS (-) lines to the data link connector (DLC). PCM connection to the DLC is typically done with a two wire, twisted pair cable used for network interconnection. The diagnostic data such as Self-test or PIDs can be accessed with a scan tool. Information on scan tool equipment is described in Section 2 , Diagnostic Methods.


High Speed - Controller Area Network (HS-CAN)
HS-CAN is based on SAE J2284, ISO-11898 and is a serial communication language protocol used to transfer messages (signals) between electronic modules or nodes. Two or more signals can be sent over one CAN network circuit allowing two or more electronic modules or nodes to communicate with each other. This communication or multiplexing network operates at 500kB/sec (kilobytes per second) and allows the electronic modules to share their information messages.

Included in these messages is diagnostic data that is outputted over the CAN High (+) and CAN Low (-) lines to the data link connector (DLC). PCM connection to the DLC is typically done with a two wire, twisted pair cable used for the network interconnection. The diagnostic data such as Self-test or PIDs can be accessed with a scan tool. Information on scan tool equipment is described in Section 2 , Diagnostic Methods.


Flash Electrically Erasable Programmable Read Only Memory
The Flash Electrically Erasable Programmable Read Only Memory (EEPROM) is an Integrated Circuit (IC) within the PCM. This IC contains the software code required by the PCM to control the powertrain. One feature of the EEPROM is that it can be electrically erased and then reprogrammed without removing the PCM from the vehicle. If a software change is required to the PCM, the module no longer needs to be replaced, but can be reprogrammed at the dealership through the DLC.


Idle Air Trim
Idle Air Trim is designed to adjust the Idle Air Control (IAC) calibration to correct for wear and aging of components. When engine conditions meet the learning requirement, the strategy monitors the engine and determines the values required for ideal idle calibration. The Idle Air Trim values are stored in a table for reference. This table is used by the PCM as a correction factor when controlling idle speed. The table is stored in Keep Alive Random Access Memory (RAM) and retains the learned values even after the engine is shut off. A Diagnostic Trouble Code (DTC) is output if the Idle Air Trim has reached its learning limits.

Whenever an IAC component is replaced or cleaned or a service affecting idle is performed, it is recommended that Keep Alive RAM be cleared. This is necessary so the idle strategy does not use the previously learned Idle Air Trim values.

To clear Keep Alive RAM, refer to PCM Reset in Section 2. It is important to note that erasing DTCs with a scan tool does not reset the Idle Air Trim table.

Once Keep Alive RAM has been reset, the engine must idle for 15 minutes (actual time varies between strategies) to learn new idle air trim values. Idle quality will improve as the strategy adapts. Adaptation occurs in four separate modes. The modes are shown in the following table.



IDLE AIR TRIM LEARNING MODES Transmission Range Air Conditioning Mode
NEUTRAL A/C ON
NEUTRAL A/C OFF
DRIVE A/C ON
DRIVE A/C OFF



Fuel Trim
Short Term Fuel Trim

If the oxygen sensors are warmed up and the PCM determines that the engine can operate near stoichiometric air/fuel ratio (14.7 to 1 for gasoline), the PCM goes into closed loop fuel control mode. Since an oxygen sensor can only indicate rich or lean, the fuel control strategy must constantly adjust the desired air/fuel ratio rich and lean to get the oxygen sensor to "switch"around the stoichiometric point. If the time between switches are the same, then the system is actually operating at stoichiometry. The desired air/fuel control parameter is called short term fuel trim (SHRTFT1 and 2) where stoichiometry is represented by 0%. Richer (more fuel) is represented by a positive number and leaner (less fuel) is represented by a negative number. Normal operating range for short term fuel trim is +/- 25%. Some calibrations will have time between switches and short term fuel trim excursions that are not equal. These unequal excursions are used to run the system slightly lean or rich of stoichiometry. This practice is referred to as using "bias". For example, the fuel system can be biased slightly rich during closed loop fuel to help reduce NOx.

Values for SHRTFT1 and 2 may change a great deal on a scan tool when the engine is operated at different rpm and load points. This is because SHRTFT1 and 2 will react to fuel delivery variability that can change as a function of engine rpm and load. Short term fuel trim values are not retained after the engine is turned off.

Long Term Fuel Trim

While the engine is operating in closed loop fuel, the short term fuel trim corrections can be "learned" by the PCM as long term fuel trim (LONGFT1 and 2) corrections. These corrections are stored in Keep Alive Memory (KAM) in tables that are referenced by engine speed and load (and by bank for engines with two HO2S sensors forward of the catalyst). Learning the corrections in KAM improves both open loop and closed loop air/fuel ratio control. Advantages include:

Short term fuel trim does not have to generate new corrections each time the engine goes into closed loop.
Long term fuel trim corrections can be used both while in open loop and closed loop modes.
Long term fuel trim is represented as a percentage, just like short term fuel trim, however it is not a single parameter. There is a separate long term fuel trim value that is used for each rpm/load point of engine operation. Long term fuel trim corrections may change depending on the operating conditions of the engine (rpm and load), ambient air temperature and fuel quality (% alcohol, oxygenates, etc.). When viewing the LONGFT1/2 PID(s), the values may change a great deal as the engine is operated at different rpm and load points. The LONGFT1/2 PID(s) will display the long term fuel trim correction that is currently being used at that rpm/load point.


Idle Speed Control Closed Throttle Determination
One of the fundamental criteria for entering rpm control is an indication of closed throttle. Throttle mode is always calculated to the lowest learned throttle position (TP) voltage seen since engine start. This lowest learned value is called "ratch," since the software acts like a one-way ratch. The ratch value (voltage) is displayed as the TPREL PID. The ratch value is relearned after every engine start. Ratch will learn the lowest, steady TP voltage seen after the engine starts. In some cases, ratch can learn higher values of TP. The time to learn the higher values is significantly longer than the time to learn the lower values. The brakes must also be applied to learn the longer values.

All PCM functions are done using this ratch voltage, including idle speed control. The PCM goes into closed throttle mode when the TP voltage is at the ratch (TPREL PID) value. Increase in TP voltage, normally less than 0.05 volts, will put the PCM in part throttle mode. Throttle mode can be viewed by looking at the TP MODE PID. With the throttle closed, the PID must read C/T (closed throttle). Slightly corrupt values of ratch can prevent the PCM from entering closed throttle mode. An incorrect part throttle indication at idle will prevent entry into closed throttle rpm control, and could result in a high idle. Ratch can be corrupted by a throttle position sensor or circuit that "drops out" or is noisy, or by loose/worn throttle plates that close tight during a decel and spring back at a normal engine vacuum.


Fail-Safe Cooling Strategy
The fail-safe cooling strategy is activated by the PCM only in the event that an overheating condition has been identified. This strategy provides engine temperature control when the cylinder head temperature exceeds certain limits. The cylinder head temperature is measured by the Cylinder Head Temperature (CHT) sensor. For additional information about the CHT sensor, refer to PCM Inputs for a description of the CHT sensor. Note: Not all vehicles equiped with a CHT sensor will have the fail-safe cooling strategy.

A cooling system failure such as low coolant or coolant loss could cause an overheating condition. As a result, damage to major engine components could occur. Along with a CHT sensor, the fail-safe cooling strategy is used to prevent damage by allowing air cooling of the engine. This strategy allows the vehicle to be driven safely for a short time with some loss of performance when a overheat condition exist.

Engine temperature is controlled by varying and alternating the number of disabled fuel injectors. This allows all cylinders to cool. When the fuel injectors are disabled, their respective cylinders work as air pumps, and this air is used to cool the cylinders. The more fuel injectors that are disabled, the cooler the engine runs, but the engine has less power.

Note: A wide open throttle (WOT) delay is incorporated if the CHT temperature is exceeded during WOT operation. At WOT, the injectors will function for a limited amount of time allowing the customer to complete a passing maneuver.

Before injectors are disabled, the fail-safe cooling strategy alerts the customer to a cooling system problem by moving the instrument cluster temperature gauge to the hot zone and a PCM DTC P1285 is set. Depending on the vehicle, other indicators, such as an audible chime or warning lamp, can be used to alert the customer of fail-safe cooling. If overheating continues, the strategy begins to disable the fuel injectors, a DTC P1299 is stored in the PCM memory, and a malfunction indicator light (MIL) (either CHECK ENGINE or SERVICE ENGINE SOON), comes on. If the overheating condition continues and a critical temperature is reached, all fuel injectors are turned off and the engine is disabled.


Failure Mode Effects Management
Failure Mode Effects Management (FMEM) is an alternate system strategy in the PCM designed to maintain engine operation if one or more sensor inputs fail.

When a sensor input is perceived to be out-of-limits by the PCM, an alternative strategy is initiated. The PCM substitutes a fixed value and continues to monitor the incorrect sensor input. If the suspect sensor operates within limits, the PCM returns to the normal engine operational strategy.

All FMEM sensors display a sequence error message on the scan tool. The message may or may not be followed by Key On Engine Off or Continuous Memory DTCs when attempting Key On Engine Running Self-Test Mode.


Engine RPM/Vehicle Speed Limiter
The powertrain control module (PCM) will disable some or all of the fuel injectors whenever an engine rpm or vehicle overspeed condition is detected. The purpose of the engine rpm or vehicle speed limiter is to prevent damage to the powertrain. The vehicle will exhibit a rough running engine condition, and the PCM will store one of the following Continuous Memory DTCs: P0219, P0297 or P1270. Once the driver reduces the excessive speed, the engine will return to the normal operating mode. No repair is required. However, the technician should clear the PCM and inform the customer of the reason for the DTC.

Excessive wheel slippage may be caused by sand, gravel, rain, mud, snow, ice, etc. or excessive and sudden increase in rpm while in NEUTRAL or while driving.




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post 3

2003 PCED OBD SECTION 2: Diagnostic Methods
Procedure revision date: 12/19/2002

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Drive Cycles
Description of OBD II Drive Cycle
The following procedure is designed to execute and complete the OBDII monitors and to clear the Ford P1000, I/M readiness code. To complete a specific monitor for repair verification, follow steps 1 through 4, then continue with the step described by the appropriate monitor found under the "OBDII Monitor Exercised" column. When the ambient air temperature is outside 4.4 to 37.8°C (40 to 100 °F), or the altitude is above 2438 meters (8000 feet), the EVAP monitor will not run. If the P1000 code must be cleared in these conditions, the PCM must detect them once (twice on some applications) before the EVAP monitor can be "bypassed" and the P1000 cleared. The EVAP "bypassing" procedure is described in the following drive cycle.

The OBDII Drive Cycle will be performed using a scan tool. Consult the instruction manual for each described function.

Note: A detailed description of a Powertrain Control Module (PCM) Reset is found in this section, refer to the table of contents.

Drive Cycle Recommendations
Most OBDII monitors will complete more readily using a "steady foot" driving style during cruise or acceleration modes. Operating the throttle in a "smooth" fashion will minimize the time required for monitor completion.
Fuel tank level should be between 1/2 and 3/4 fill with 3/4 fill being the most desirable.
The Evaporative Monitor can only operate during the first 30 minutes of engine operation. When executing the procedure for this monitor, stay in part throttle mode and drive in a smooth fashion to minimize "fuel slosh".
WARNING: STRICT OBSERVANCE OF POSTED SPEED LIMITS AND ATTENTION TO DRIVING CONDITIONS ARE MANDATORY WHEN PROCEEDING THROUGH THE FOLLOWING DRIVE CYCLES.

For best result, follow each of the following steps as accurately as possible:



OBDII Monitor Exercised Drive Cycle Procedure Purpose of Drive Cycle Procedure
Drive Cycle Preparation 1. Install scan tool. Turn key on with the engine off. Cycle key off, then on. Select appropriate Vehicle & Engine qualifier. Clear all DTC's/Perform a PCM reset. Bypass engine soak timer. Resets OBDII Monitor status.
2. Begin to monitor the following PIDs: ECT, EVAPDC, FLI (if available) and TP MODE. Start vehicle WITHOUT returning to Key Off.
3. Idle vehicle for 15 seconds. Drive at 64 Km/h (40 MPH) until ECT is at least 76.7°C (170°F).
Prep for Monitor Entry 4. Is IAT within 4.4 to 37.8°C (40 to 100°F)? If not, complete the following steps, but note that step 14 will be required to "bypass" the EVAP monitor and clear the P1000. Engine warm-up and provide IAT input to the PCM.
HEGO 5. Cruise at 64 Km/h (40 MPH) for at least 5 minutes. Executes the HEGO monitor.
EVAP 6. Cruise at 64 to 128 Km/h (45 to 65 MPH) for 10 minutes (avoid sharp turns and hills). NOTE: To initiate the monitor TP MODE should = PT, EVAPDC must be > 75%, and FLI must be between 15 and 85%. Executes the EVAP monitor (If IAT is within 4.4 to 40°C (40 to 120°F).
Catalyst 7. Drive in stop-and-go traffic conditions. Include five different constant cruise speeds, ranging from 32 to 112 Km/h (20 to 70 MPH) over a 10 minute period. Executes the Catalyst Monitor.
EGR 8. From a stop, accelerate to 72 Km/h (45 MPH) at 1/2 to 3/4 throttle. Repeat 3 times. Executes the EGR Monitor.
SEC AIR/CCM (Engine) 9. Bring the vehicle to a stop. Idle with transmission in drive (neutral for M/T) for 2 minutes. Executes the ISC portion of the CCM.
CCM (Trans) 10. For M/T, accelerate from 0 to 80 Km/h (0 to 50 MPH), continue to step 11. For A/T, from a stop and in overdrive, moderately accelerate to 80 Km/h (50 MPH) and cruise for at least 15 seconds. Stop vehicle and repeat without overdrive to 64 Km/h (40 MPH) cruising for at least 30 seconds. While at 64 Km/h (40 MPH), activate overdrive and accelerate to 80 Km/h (50 MPH) and cruise for at least 15 seconds. Stop for at least 20 seconds and repeat step 10 five times. Executes the transmission portion of the CCM.
Misfire & Fuel Monitors 11. From a stop, accelerate to 104 Km/h (65 MPH). Decelerate at closed throttle until 64 Km/h (40 MPH) (no brakes). Repeat this 3 times. Allows learning for the misfire monitor.
Readiness Check 12. Access the On-Board System Readiness (OBDII monitor status) function on the scan tool. Determine whether all non-continuous monitors have completed. If not, go to step 13. Determines if any monitor has not completed.
Pending Code Check and EVAP Monitor "Bypass" Check 13. With the scan tool, check for pending codes. Conduct normal repair procedures for any pending code concern. Otherwise, rerun any incomplete monitor. If the EVAP monitor is not complete AND IAT was out of the 4.4 to 37.8 °C (40 to 100 °F) temperature range in step #4, or the altitude is over 2438 m. (8000 ft.), the EVAP "bypass" procedure must be followed. Proceed to Step 14. Determines if a pending code is preventing the clearing of P1000.
EVAP Monitor "Bypass" 14. Park vehicle for a minimum of 8 hours. Repeat steps 2 through 12. DO NOT REPEAT STEP 1. Allow the "bypass" counter to increment to two.





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post 4

2003 PCED OBD SECTION 2: Diagnostic Methods
Procedure revision date: 12/19/2002

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Powertrain Control Module (PCM) Reset
Description
All OBDII scan tools support the powertrain control module (PCM) reset.

The PCM Reset allows the scan tool to command the PCM to clear all emission-related diagnostic information. When resetting the PCM, a DTC P1000 will be stored in the PCM until all the OBD II system monitors or components have been tested to satisfy a drive cycle, without any other faults occurring. For more information about a drive cycle, refer to Drive Cycles .

The following events occur when a PCM reset is performed:

Clears the number of Diagnostic Trouble Codes (DTCs).
Clears the DTCs.
Clears the freeze frame data.
Clears diagnostic monitoring test results.
Resets status of the OBD II system monitors.
Sets DTC P1000.

Resetting Keep Alive Memory (KAM)
Resetting Keep Alive Memory will return PCM memory to its default setting. Adaptive learning contents such as idle speed, refueling event, and fuel trim are included. A PCM Reset (described above) is also part of a KAM Reset. Both can be useful in post repair retest.

After Keep Alive Memory has been reset, the vehicle may exhibit certain driveability concerns. It will be necessary to drive the vehicle to allow the PCM to relearn values for optimum driveability and performance.

This function may not be supported by all scan tools. Refer to scan tool manufacturer's instruction manual.

If an error message is received or the scan tool does not support this function, disconnecting the battery ground cable for a minimum of 5 minutes may be used as an alternative procedure.




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post 5

2003 PCED OBD SECTION 2: Diagnostic Methods
Procedure revision date: 12/19/2002

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Adaptive Fuel DTCs Diagnostic Techniques
Adaptive Fuel DTCs Diagnostic Techniques help isolate the root cause of the adaptive fuel concern. Before proceeding, attempt to verify if any driveability concerns are present. These diagnostic aids are meant as a supplement to the pinpoint test steps in Section 5. For a description of fuel trim, refer to Section 1 , Powertrain Control Software, Fuel Trim.

Obtain Freeze Frame Data

Freeze Frame Data can be helpful in duplicating and diagnosing adaptive fuel concerns. This data (a snapshot of certain PID values, recorded at the time the DTC was stored in Continuous Memory) is helpful to determine how the vehicle was being driven when the fault occurred, and can be especially useful on intermittent concerns. Freeze Frame Data, in many cases, can help to isolate possible areas of concern as well as rule out others. Refer to Freeze Frame Data in this section for a more detailed description of this data.

Using the LONGFT1 and LONGFT2 (dual bank engines) PIDs

The LONGFT1/2 PIDs can be useful for diagnosing fuel trim concerns. A negative PID value indicates that fuel is being reduced to compensate for a rich condition, while a positive PID value indicates that fuel is being increased to compensate for a lean condition. It is important to know that there is a separate LONGFT value that is used for each rpm/load point of engine operation. When viewing the LONGFT1/2 PIDs, the values may change a great deal as the engine is operated at different rpm and load points. This is because the fuel system may have learned corrections for fuel delivery concerns that can change as a function of engine rpm and load. The LONGFT1/2 PIDs will display the fuel trim currently being used at that rpm and load point. Observing these changes in LONGFT1/2 can help when diagnosing fuel system concerns. For example:

A contaminated MAF sensor would result in matching LONGFT1/2 correction values that are negative at idle (reducing fuel), but positive (adding fuel) at higher rpm and loads.
LONGFT1 values that differ greatly from LONGFT2 values would rule out concerns that are common for both banks (for example, fuel pressure concerns, MAF sensor, etc. could be ruled out).
Vacuum leaks would result in large rich corrections (positive LONGFT1/2 value) at idle, but little or no correction at higher rpm and loads.
A plugged fuel filter will result in no correction at idle, but large rich corrections (positive LONGFT1/2 value) at high rpm and load.
Resetting Long Term Fuel Trims

Long term fuel trim corrections can be reset by resetting the PCM Keep Alive Memory (KAM). Refer to Resetting Keep Alive Memory in this section to reset KAM. After making a fuel system repair, KAM must be reset. For example, if dirty/plugged injectors cause the engine to run lean and generate rich long term corrections, replacing the injectors and not resetting KAM will now make the engine run very rich. The rich correction will eventually be "learned out" during closed loop operation, but the vehicle may have poor driveability and have high CO emissions while it is learning.

P0171/P0174 System Too Lean Diagnostic Aids

Note: If the system is lean at certain conditions, then the LONGFT PID would be a positive value at those conditions, indicating that increased fuel is needed.

The ability to identify the type of lean condition causing the concern can be crucial to a correct diagnosis.

Air Measurement System:

With this condition, the engine may actually run rich or lean of stoichiometry (14.7:1 air/fuel ratio) if the Powertrain Control Module (PCM) is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine would run lean at higher rpm because the PCM would deliver fuel for less air than is actually entering the engine.

Examples: MAF sensor measurement inaccurate (corroded connector, contamination/dirty (a contaminated MAF sensor will typically result in a rich system at low airflows (PCM will reduce fuel) and a lean system at high airflows (PCM will increase fuel), etc).

Vacuum Leaks/Unmetered Air:

With this condition, the engine may actually run lean of stoichiometry (14.7:1 air/fuel ratio) if the Powertrain Control Module (PCM) is not able to compensate enough to correct for the condition. This condition can be caused by unmetered air entering the engine, or due to a MAF malfunction. In this situation, the volume of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. Vacuum leaks will normally be most apparent when high manifold vacuum is present (for example, during idle or light throttle). If freeze frame data indicates that the fault occurred at idle, a check for vacuum leaks/unmetered air might be the best starting point.

Examples: Loose, leaking or disconnected vacuum lines, intake manifold gaskets or o-rings, throttle body gaskets, brake booster, air inlet tube, stuck/frozen/aftermarket PCV valve, unseated engine oil dipstick, etc.

Insufficient Fueling:

With this condition, the engine may actually run lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. This condition can be caused by a fuel delivery system concern that restricts or limits the amount of fuel being delivered to the engine. This condition will normally be most apparent when the engine is under a heavy load and at high rpm, when a higher volume of fuel is required. If freeze frame data indicates that the fault occurred under a heavy load and at higher rpm, a check of the fuel delivery system (checking fuel pressure with engine under a load) might be the best starting point.

Examples: low fuel pressure (fuel pump, fuel filter, fuel leaks, restricted fuel supply lines), fuel injector concerns, etc.

Exhaust System Leaks:

In this type of condition, the engine may actually be running rich of stoichiometry (14.7:1 air / fuel ratio) because the fuel control system is adding fuel to compensate for a perceived (not actual) lean condition. This condition is caused by oxygen (air) entering the exhaust system from an external source. The HO2S will react to this exhaust leak by increasing fuel delivery. This condition will cause the exhaust gas mixture from the cylinder to be rich.

Examples: Exhaust system leaks upstream or near HO2S, poorly welded/leaking HO2S boss, malfunctioning Secondary Air Injection system, etc.

P0172/P0175 System Too Rich Diagnostic Aids

Note: If the system is rich at certain conditions, then the LONGFT PID would be a negative value at that airflow, indicating that decreased fuel is needed.

System rich concerns are usually caused by fuel system concerns, although the MAF sensor, and base engine (for example, engine oil contaminated with fuel) should also be checked.

Air Measurement System:

With this condition, the engine may actually run rich or lean of stoichiometry (14.7:1 air/fuel ratio) if the Powertrain Control Module (PCM) is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually less than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine would run rich at idle because the PCM would deliver fuel for more air than is actually entering the engine.

Examples: MAF sensor measurement inaccurate (corroded connector, contamination/dirty (a contaminated MAF sensor will typically result in a rich system at low airflows (PCM will reduce fuel) and a lean system at high airflows (PCM will increase fuel), etc.).

Fuel System:

With this condition, the engine may actually run rich of stoichiometry (14.7:1 air/fuel ratio) if the Powertrain Control Module (PCM) is not able to compensate enough to correct for the condition. This situation can be caused by a fuel delivery system that is delivering excessive fuel to the engine.

Examples:

Fuel pressure regulator causes excessive fuel pressure (system rich at all airflows)(fuel pressure can be intermittent, going to pump deadhead pressure, then returning to normal after engine is turned off then restarted).
Fuel pressure regulator vacuum hose off (causes excessive fuel pressure at idle, system rich at idle airflows).
Fuel pressure regulator diaphragm ruptured (fuel leaking into intake manifold, system rich at lower airflows).
Fuel return line crimped/damaged (fuel pressure high, system rich at lower airflows).
Fuel injector leaks (injector delivers extra fuel).
EVAP canister purge valve leak (if canister is full of vapors, introduces extra fuel).
Fuel rail pressure sensor (electronic returnless fuel systems) concern causes sensor to indicate lower pressure than actual. PCM commands higher pressure to the fuel pump driver module (FPDM), causing high fuel pressure (system rich at all airflows).
Base Engine

Engine oil contaminated with fuel can contribute to a rich running engine.




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sorry about that im going out today, you should now know more than most on o2s,,,,,,most likely the rf o2 is bad but do both anyway . if you can monitor with that type of scanner now is a good time to learn what its doing???????

woa woa woa....lets not get ahead of ourselfs here. you have a misfire somewhere in the engine right? do you know what you are looking at on the scan tool? if you have a misfire the o2 sensor readings will be bad because there is a ton of raw fuel going into exhaust. you have to try to figure out your misfire first before you condemn an o2. my guess is you have an ignition problem...either plugs or wires/boots. depending on the year of the car and what scanner your using it may tell you exactly what cylinder is misfiring. if you haven't done a tune in awhile i would start with that. (plugs, wires, fuel filter, air filter, pcv, clean maf with approved solvent, etc.) then start from scratch. you may not need o2 sensor. have to fix mechanical part of problem before you start believing sensors. good luck and if you need more help just post.

My engine threw a lean code at me about two years ago and after all was said and done, it turned out it was the evap canister purge valve. Don't ask my how that happened, I have no idea. Swapped out the purge valve and all was taken care of. Two years later I have a hitching/stumbling problem.... swapped out upstream o2 sensors and problem solved. hope it helps

in my 6 odd years of drivablility work i have replaced only a handful of computers to fix problems. it is a possibility but there are so many other things that need to be checked first. in all seriousness man you may be a little over your head and before you hurt your car just take it to a shop and let them figure out the problem. at the very least they can figure it out and then you can take the car back and fix it yourself. i think you either got a maf issue or a vacuum leak somewhere in the system. like stated above it could be your evap purge soleniod, intake gasket, egr, vacuum hose, etc. etc. it's just hard to get you pointed in a direction when we arent there you know?

i can see you havent read about code,,,1131 is not a lean code.....all those codes are for 02s. each is a different fuction of the o2s.. your o2s have alot to do with driveability,your o2 not switching is like a misfire/sputter,,your trans can pick that up and thats what your feeling.read above the codes and it tells you what switching is..if you still feel you have a lean code i can post what ford would do for diagnostic on that,,,