another way to pull codes?

90lxfoxbody · Jul 23, 2007

my car started bucking/missing badly recently. i have checked everything i know to check and it still does it, driving me freaking nuts. i tried to pull the codes, but apparently my check engine bulb is blown. is there another way to pull the codes?

the scenario; i was driving around town, taking care of business. hot day outside. i got home, parked the car and then about an hour later came back out to go somewhere. can was running fine an hour before, but when i cranked it back up it started bucking and acting like it was about to cut out on me. almost impossible to keep it at a steady rpm. runs like crap, total pain to drive. i can only imagine what my mileage is right now.

i checked the plugs, plug wires, dist cap, rotor button, air fulter, fuel filter, iac, tps, throttle body, removed upper intake and checked the gaskets and all lines for vac leaks, checked fuel pump, ec. the smog control and egr were removed years before, as well as the o2 sensors. i have listened closely to the fuel pump while the car is running, and it hums consistently, no stuttering or cutting out. i checked my ignition coil, coil wire, still nothing out of the ordinary.

so my question, if i were to remove the maf sensor while the car is running, should the car cut off or what? i unplugged the maf sensor and the car didn't run much differently. same thing for the fuel pressure regulator. any ideas??? i have a kit for rebuilding my injectors. could a bad or clogged injector cause this? i called auto zone and was told that they can only run diagnostic checks on 1996 cars and up. so, it's driving me nuts, runs like crap and it bucks and jumps so much it beats the hell out of me to drive it.

93lxdm78 · Jul 23, 2007

Check your maf make sure its clean and pluged in all the way. Use brake clean and spray it out sounds like a maf issue. Also make sure the wires around the maf aren't damaged.

Good Luck

jrichker · Jul 23, 2007

Use the first method for 86-88 model Mustangs. It will work if the check engine light is burned out.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See http://www.troublecodes.net/Ford/

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

90lxfoxbody · Jul 23, 2007

i checked the wiring plug that goes into the maf, and the connectors seem to have some white crud on them, possubly corrosion. not terribly bad, but noticable. what would be the best way to clean inside the tiny little connector slots? would it hurt to spray cleaner in there? also, could that be the culprit? seems very minor for such a drastic difference in performance.

jrichker · Jul 24, 2007

I woul really recommend dumping the codes before you do anything else. It will reduce the amount of time you spend chasing non-productive rabbits.

I use a jeweler's screwdriver to scrape the contacts. Use non-flammable brake parts cleaner to clen them. It is the same stuff as electrical parts cleaner in a bigger can. It is cheaper too.

90lxfoxbody · Jul 27, 2007

JRichker i need your genius, fuel pump issues

ok, this is frustrating, to the N th degree. Last thursday I went into town and stopped a few places, and my car was running perfect. I mean letter perfect. I get complements all the time on the car, especially for the way it sounds. I went home and parked the car, then about an hour later I came back out and got in to go back into town. The car ran like crap, jumping and bucking. It has a horrible miss, and while it is running it will not stay at a steady rpm and the tach is bouncing all over the place. basically it beats the hell out of me while i am driving it.

So. the first dilemma, as per Jrichker's advice, I tried to dump the codes. Problem is, my check engine light is apparently blown. Is there another way to pull the codes without using the check engine light? Keep in mind i am going through a very nasty separation, and I am pissant BROKE, i mean never been this broke in my life broke. I don't have the $ to pick up a code reader from auto zone kinda broke.

Next, let me list what i have checked.

Plugs and wires, all in good shape. all my plugs are the same color and have no crud, buildup etc. Matter of fact, all eight of them look pretty damned perfect. If you were to look in an ASE manual at a picture of perfect plugs, this is what they look like.

Distributor cap and rotor button are recently installed and look great, no crap on the button or contacts.

Ignition coil seems to be fine, new coil wire, started solenoid and all connected elements seem to be fine, physically checked each wire.

Replaced the tps, one of the plactic teeth on the inside was worn down so I put a new one on.

Checked the maf, vanes are clean. The electrical connector contacts were a bit dirty but I cleaned them up and the problem persisted.

My egr and smog control items were removed about seven years ago when the engine was rebuilt. never caused a problem before so i doubt it is involved now. the engine was rebuilt by a very reputable guy who builds and races mustangs.

Checked every inch of vacuum line, all vacuum caps, pcv valve to intake, etc etc, all fine.

the fuel injectors look fine, with no odor of gasoline while running or not, and no physical damage to the injectors or wires is visible.

The fuel pump relay kicks on when I turn on the swith, and i can hear the fuel pump prime.

Now here's the hinky part. I pulled the mat in the hatchback out of the way, and held my head close to the fuel pump while the car was running, and the fuel pump makes this humming noise when it is working. when the car would stumble and miss, the fuel pump noise would surge and fall with it. naturally that makes the fuel pump suspect. i have never changed the fuel pump in this car, and i think it came with a screen on it that is inside the tank, so it is possible i am working with an 18 year old fuel pump. so i guess at this point the question is this:

if the fuel pump surges when the engine stumbles, but it has constant power and the realy works fine, if it's not a bad fuel pump, what could cause it to surge??

damn, i'm tired just from typing this. flex your big sexy brains everyone, i really need to get this fixed, it happens at the worst possible time.

and thanks, as always.

jrichker · Jul 27, 2007

You can dump the codes without a working check engine light. Use the 86-88 method...

You watch the flashing test lamp or Check Engine Light and count the flashes.

See http://www.troublecodes.net/Ford/

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Look for codes 95 & 96 - they are related to the fuel pump wiring.

90lxfoxbody · Jul 27, 2007

ok great, will do. i will need to get the stuff to fabricate a test light. in the mean time, can you speculate why the fuel pump would surge? is that typical of a dying fuel pump, or do they usually just up and quit?

jrichker · Jul 27, 2007

I replaced one that simply died, it just quit.

Since money is a little tight for you right now, spend a little more time doing some diagnosis before swapping parts. It will help the budget.

Look for the 95 or 96 codes and if you find them, remove the driver's seat and inspect the relay socket and wiring. If it is good, then replace the relay.

The quality of the wiring between the pump and the connection to the mounting plate is often questionable. Mine was some slip connects covered by some cheap looking plastic tubing. It looked all too easy for it to slip and slide around and make sparks. Boom! no more Mustang...

873Stang · Jul 28, 2007

if you have or know someone with a fuel pressuser gauge id check it with the car running to see if the prussure drops at all or a certain point i beleave its spose to be at 35psi some one can correct me if im wrong. good luck p.s. if you do end up replacing the pump dont forget to get the screen and fuel filter.

90lxfoxbody · Jul 28, 2007

pulled codes, need help with diagnosis

Ok, finally got my hands on a scanner, worked like a charm. Got a few codes, as follows.

31 - EVP - EVP signal is/was out of range - EVP - EGR valve position
the egr was eliminated with all the smog control when the engine was rebuilt six or seven years ago. never had this isssue since so i doubt this is it.

66 - Vane Air Flow (VAF) or Mass Air Flow (MAF) signal low - VAF MAF

67 - Park/Neutral circuit fault - PNP

85 - 2 3L T/C Automatic - 3/4-4/3 Shift solenoid - Transmissions - adaptive lean limit reached in fuel control program

91 - System running lean - Fuel control

96 - Fuel pump monitor circuit shows no power - Power / Fuel Pump Circuits

so, given the symptoms ( bucking, missing, etc etc ) and these codes, i think it clearly points to a fuel issue, so what is the next step? the relay kicks over, but can a relay go bad without quitting altogether, or is the fuel pump itself clearly the problem? it still primes and i can hear it running, but it surges and pulsates.

i really need tgo get this fixed, it couldn't come at a worse time!

90lxfoxbody · Jul 28, 2007

ok, just remembered i have a spare fuel pump relay. swapped them out and it runs the same, so that eliminates the relay

90lxfoxbody · Jul 28, 2007

... at this point all i can say is WHAT THE *****!?!?!? i checked the inertia switch, it's getting power, 12 volts everywhere i check, so does anyone have the slightest idea what this can be? i mean someone had had this problem before?

jrichker · Jul 28, 2007

CODE: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference
voltage supplied by the computer) missing or broken wire or bad connection in circuit.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5
volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the
center of the car. Use the black/white wire for the ground for the DVM.

With the sensor removed from the EGR and still connected, press the plunger and watch
the voltage change on the brown/lt green wire. Pull the passenger side kick panel and
measure the voltage at the computer. You will need to remove the plastic cover over the
wires and probe them from the backside. A safety pin may prove very useful for this task.
Use pin 27, EVR input (brown/lt green wire) and pin 46, signal ground (black/white wire)
to measure the voltage. The orange/white wire is Vref and should always be 5 volts -/+
.25 volt. Be sure to measure Vref at the EGR sensor to rule out any broken wires or bad
connections.

Code 66 MAF below minimum test voltage.
Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring,
missing power to MAF. Check for missing +12 volts on this circuit. Check the two links
for a wiring diagram to help you find the red wire for computer power relay switched +12
volts. Check for 12 volts between the red and black wires on the MAF heater (usually
pins A & B). while the connector is plugged into the MAF. This may require the use of a
couple of safety pins to probe the MAF connector from the back side of it.

There are three parts in a MAF: the heater, the sensor element and the amplifier. The
heater heats the MAF sensor element causing the resistance to increase. The amplifier
buffers the MAF output signal and has a resistor that is laser trimmed to provide an
output range compatible with the computer's load tables.

The MAF element is secured by 2 screws & has 1 wiring connector. To clean the
element, remove it from the MAF housing and spray it down with electronic parts cleaner
or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).

The MAF output varies with RPM which causes the airflow to increase or decease. The
increase of air across the MAF sensor element causes it to cool, allowing more voltage to
pass and telling the computer to increase the fuel flow. A decrease in airflow causes the
MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow.
Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and
tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by
measuring across the pins and not between the pins and ground.

At idle = approximately .6 volt
20 MPH = approximately 1.10 volt
40 MPH = approximately 1.70 volt
60 MPH = approximately 2.10 volt

Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the
computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin
9 on the computer (tan/light blue wire) should be less than 2 ohms.

There should be a minimum of 10K ohms between either pin C or D on the MAF wiring
connector and ground. Make your measurement with the MAF disconnected from the
wiring harness.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring
http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel pump, alternator, ignition & A/C wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Computer,. actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Fuse panel layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Vacuum routing
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

Code 67 - clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C
in On position when codes where dumped. Possible neutral safety switch or wiring
problem. This code may prevent you from running the Key On Engine On tests. You can
generally ignore this code, since it has no effect on engine performance.

The computer wants to make sure the A/C is off due to the added load on the engine for
the engine running tests. It also checks to see that the transmission is in Neutral and the
clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the car from being
driven while the computer is in test mode. Key On Engine Running test mode takes the
throttle control away from the driver for several tests. This could prove hazardous if the
computer was jumpered into test mode and then driven.

The NSS code 67 can be bypassed for testing. You will need to temporarily ground
computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the
passenger side kick panel and then remove the plastic cover from the computer wiring
connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to
the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!

Code 85 - CANP solenoid - The Carbon Canister solenoid is inoperative. Check
vacuum lines for leaks and cracks. Check electrical wiring for loose connections,
damaged wiring and insulation. Check solenoid valve operation by grounding the
gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is
always energized any time the ignition switch is in the run position.

Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the
rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side
of the solenoid valve connects to one side of the canister. The other side of the canister
connects to a rubber hose that connects to a line that goes all the way back to the gas
tank. There is an electrical connector coming from the passenger side injector harness
near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas
tank. The solenoid valve opens at cruse to provide some extra fuel.

It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP
& keeps the car from smelling like gasoline in a closed garage. So with all these good
things and no bad ones, why not hook it up & use it?

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2
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
0.2 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
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.

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.

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

Code 96 – KOEO- Fuel pump monitor circuit shows no power - Fuel pump relay
or battery power feed was open - Power / Fuel Pump Circuits. The fuel pump lost power
at some time while the ignition switch was in the run position.

Look for a failing fuel pump relay, bad connections or broken wiring. The fuel pump
relay is located under the Mass Air Meter on Fox bodied stangs built after 91. On earlier
model cars is under the passenger seat. On Mass Air Conversions, the signal lead that
tells the computer that the fuel pump has power may not have been wired correctly. See
http://www.stangnet.com/tech/maf/massairconversion.html

Diagram courtesy of Tmoss & Stang&2birds

Look for power at the fuel pump - the fuel pump has a connector at the rear of the car
with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should
be hot when the test connector is jumpered to the test position. .

To trick the fuel pump into running, find the ECC test connector and jump the connector in the
lower RH corner to ground.

86-90 Models:
Using the diagram, check the red/black wire from the fuel pump relay: you should see 12
volts or so. If not, check the inertia switch: on a hatch it is on the drivers side by the
taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up
the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both
sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the
fuel pump. Good voltage there, then the fuel pump is the likely culprit since it is getting
power. No voltage there, check the Orange/Lt blue wire, it is the power feed to the fuel
pump relay & has a fuse link in it. Good voltage there & at the Pink/black wire, swap the
relay.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

90lxfoxbody · Jul 28, 2007

ok, back to square 1, but now the problem is getting WORSE. the engine will not rev past 250 - 3000 rpm's. spent a solid hour testing wires with a meter, power to everything. any ideas at all? everything points to a lean running condition.... this is absolutely hair pulling

jrichker · Jul 28, 2007

Check your fuel pressure first, 37-41 PSI at idle, vacuum line disconnected from the fuel pressure
regulator and plugged. Test gauges are available for rent/loan at most big auto parts stores.

A bad MAF will cause a lean condition. Since you got a 66 code, clear the codes and recheck.

The code 91 can be caused by a vacuum leak, so a vacuum gauge to check for low vacuum is helpful.

90lxfoxbody · Jul 29, 2007

inertia switch??

to make a long story short, i have a nasty fuel problem. car runs like CRAP, won't idle, bucking, missing, total terror to try and drive. i have checked everything, pulled codes, etc etc. i was checking the power to the fuel pump, relay and inertia switch and noticed that the red button on the inertia switch is permanantly in the down position, if you push it, it doesn't move all. is it supposed to be that way? the switch was a little loose so i tightened it up but afterward the car ran the same. getting the car fixed today would be a huge shot in the arn. any input anyone???

StangItMan · Jul 29, 2007

reply

Inertia switch down allows closed circuit ... fuel pump getting voltage >>> ok <<<

When working to kill 12v the red will be up ... tap the switch with handle end of screwdriver, it should pop up/out. Push back in to get 12v again for pump.

90lxfoxbody · Jul 29, 2007

new codes - more confusion

ok, took another shot at figuring my problem out. to recap, car is running like crap, missing, bucking, terrible to drive. got a scanner, pulled codes, they led me nowhere. i checked and rechecked everything with a meter and i am getting power everywhere as it should. i disconnected the battery to clear the codes and ran the code scanner again. i performed one KOEO test and tried to perform a KOER test, but the car will not stay running.

these are the codes i got with the KOEO test:

31 - egr - was removed with somg control parts abiut six or seven years ago, so this is not a suspect

67 - neutral drive/gear switch - neutral pressure switch - none of these are suspects, given the symptoms

85 - cannister purge - not likely - lean limit reached in fuel control program - i think this is symptomatic of something else

43 - ego sensor - exhaust gas oxygen. my car hasn't had o2 sensors since the smog control was removed years ago. this is a new code i wasn't getting the first time

66 - Mass air flow sensor or vane air flow sensor - voltage too low. this is a new code also.

before i was getting a p6 code, but after i cleared the codes and retested it, i got no 96 codes after two tries. so i think the 66 code will lead me in the right direction.

any input?

and thanks ahead jrichker, you've been a great help.

jrichker · Jul 29, 2007

No O2 sensors is not a good thing. The computer depends on the O2 sensors for information to measure fuel control on everything from idle to cruse. At WOT, it does not use input from the O2 sensors.

Code 66 MAF below minimum test voltage.
Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring, missing power to MAF. Check for missing +12 volts on this circuit. Check the two links for a wiring diagram to help you find the red wire for computer power relay switched +12 volts. Check for 12 volts between the red and black wires on the MAF heater (usually pins A & B). while the connector is plugged into the MAF. This may require the use of a couple of safety pins to probe the MAF connector from the back side of it.

There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables.

The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).

The MAF output varies with RPM which causes the airflow to increase or decease. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow. Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.

At idle = approximately .6 volt
20 MPH = approximately 1.10 volt
40 MPH = approximately 1.70 volt
60 MPH = approximately 2.10 volt

Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin 9 on the computer (tan/light blue wire) should be less than 2 ohms.

There should be a minimum of 10K ohms between either pin C or D on the MAF wiring connector and ground. Make your measurement with the MAF disconnected from the wiring harness.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel pump, alternator, ignition & A/C wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Computer,. actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Fuse panel layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Vacuum routing
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

another way to pull codes?

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