More friggin codes

Code 11 The computer's internal self test passed. The computer thinks it is OK and any problems present are in the external sensors.


Code 64 – ACT (Air Charge Temperature) signal low or grounded. Bad sensor,
sensor wiring on pin 25 shorted to ground, or bad computer.

Note that all resistance tests must be done with power off. Measuring
resistance with a circuit powered on will give false readings and possibly
damage the meter.

The ACT is located in the #5 intake runner on Mustangs built from 86-93.
Disconnect the sensor by removing the sensor wiring connector. Measure
the resistance across the sensor pins.

Ohms measures at the computer with the computer disconnected, or at the
sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

If the sensor resistances read good according to the table, remove
the passenger side kick panel and disconnect the computer connector.
A single 10 MM bolt secures the connector in place. With the sensor
connector still disconnected, measure the resistance between pin 25
(lt green/pink wire) and ground. If you wish, you can make your
measurements at the ACT sensor end. This will save you from
counting the computer connector pins to locate the correct one.
However, you will still have to disconnect the computer connector.
You should see 100K Ohms or greater between pin 25 and ground.
Less than that indicates wiring problems with the pin 25
lt green/pink wire shorted to ground. Note that the following
diagram on the connector displays the pins viewed from the
computer side.



See following website for some help from Tmoss
(diagram designer) & Stang&2Birds (website host) for
help on 88-95 wiring Mustang FAQ - Engine Information
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Diagram courtesy of Tmoss & Stang&2birds



Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves.
When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and
the O2 readings increase. By toggling the dump valve (TAB) and switching the diverter valve (TAD) flow from the
back of the heads to the air pipe, the computer tests for the 44/94 codes.

Testing the system:
Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect
the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump
the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or
to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the
vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes
from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the
vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire.
Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to
the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground
necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side
will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel &
the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum
to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin
32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine
with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after
doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to
ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the
solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38
and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin
38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the
solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power &
ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them

Do the tests to apply vacuum to the diverter valves and see what happens...

ACT problem:
Check the end to end resistance of the ACT sensor to computer wiring. You should see less than 2 Ohms on each wire. Put one probe on the ACT sensor wire and the other on the computer pin it connects to. Use the diagram I posted to find the wire colors and pin numbers.

Code 94/44 problem
Use a vacuum gauge to check for vacuum at the solenoid valves with the engine running. Tap into the vacuum system at the vacuum tree and apply vacuum directly to the bypass valve and then the diverter valve to be sure they change the airflow through them.

General advice when using an Ohmmeter:
Always have the power turned off on a circuit when you use the Ohms function on your meter. Have the ignition switch turned off, or remove the fuse (if there is one) or disconnect the battery negative terminal. This protects the meter from damage and helps prevent inaccurate readings. Keep your fingers from touching the probe tips when making the measurements because it will often cause inaccurate results.

The failure of the end to end resistance check means the wiring or connections for the ACT are bad. Try wiggling the wires when you do resistance checks to spot intermittent connections.



Use the diagram of the 10 pin connectors and try measuring between the engine side white 10 pin connector pin 6 and the LT green/pink wire on the ACT. There should be less than 2 ohms.

Do the same with the ACT black/white wire and pin 1 of the engine side white 10 pin connectors. There should be less than 2 ohms.

Do an end to end resistance check from the computer connector pin 25 to pin 6 on the body side of the white 10 pin connector. There should be less than 2 ohms.

Do an end to end resistance check from the computer connector pin 46 to pin 1 on the body side of the white 10 pin connector. There should be less than 2 ohms.

If all the resistance checks are good, then the 10 pin connector contacts are not making a good connection. Clean the 10 pin connectors with non-flammable brake parts cleaner and try to reshape the pins and sockets to make a better connection. A small jeweler's screwdriver is useful for this job.

Code 41 or 91 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

Revised 22-Jun-2009 to include 3 digit code and wiring for 94-95 5.0 Mustangs

Code 41 is a RH side sensor,
Code 91 is the LH side sensor.

Code 172 is the RH side sensor
Code 176 is the LH side sensor

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Testing the O2 sensors 87-93 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Testing the O2 sensors 94-95 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.
A secondary problem with only a code 41 is for cars with an intact smog pump and cats. If the tube on the back of the heads clogs up the driver’s side, all the air from the smog pump gets dumped into one side. This excess air upsets the O2 sensor calibration and can set a false code 41. The cure is to remove the crossover tube and thoroughly clean the insides so that there is no carbon blocking the free flow of air to both heads.

Code 91 takes control over the thermactor codes. If the Thermactor problem wasnt fixed, once you fix the Code 91 the Thermactor codes will show back up. The 02 sensors cant detect check both problems at once.

It sounds like the 02 went bad while all this was going on. If you wanna rule out a bad 02 sensor, just remove the drivers side 02 and put in the passenger side. Same for the passenger 02. If code 41 shows, then the Driver side 02 is bad. If 91 shows, then its a wiring Issue or an actuall LEAN Code.

If you get this code 91 solved, and 94 and 44 show back up, you may need to check the Crossover tube on the back of the heads

Cool.....good luck

Id say it could be an ignition problem. Under load is when a ignition problem will show its face the majority of the time. Id be checking the simple things first. Plugs, Wires, cap and rotor. Hows your fuel pressure? And to be accurate the Fuel pressure would need to monitored while the symptom is present.

Check the crossover tube for being clogged like i mentioned earlier. Ive never seen it affect drivability though

If there is any way you can bypass the Crane box and run the stock set up, Id try that. You said the vacuum went down a tad, and that can be caused by an ignition problem.