Electrical 93 hatch 4cyl auto swapped to t5 5.0 cant retrieve codes

I have used all the diag info from all the different threads and still cant read codes. cel is only lit when key is moved to start position. when you jump the dlc for codes it clicks turns fuel on an off but no codes. checked with test light, dash cel and anolog meter nothing worked. car runs fine no 11 or 111 or anything I have all 93 correct harnesses except trans(still auto harness) neutral and clutch switch bypassed. A3M ecu, I repaired a fried 46 trace and 1 capasitor on the edge of the board. Im to Nervous to attemped the other 2, they look ok. I chased all wiring down continuity is good everywhere like 0.1 ohms max, could the last 2 unrepaired caps make it not blink codes?or maybe 140 cluster swap messing with it? test light method has the light solid on, same with cheap scanner, but cel in car is never on except when key is in start position... should i just buy a microsquirt. Anyone have a A3M ecu for sale? Thanks in advance
 
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The A9L for 5 speed Is drop in swap for a A3M
Using an unmodified Auto Trans O2 sensor harness with a 5 speed computer will fry the trace inside the computer for pin 46..

Computer & interchange information for 5.0 Mustang

Revised 16-Oct-2011 to add O2 sensor harness warnings

The Mass Air computers from 89-93 are interchangeable with a few exceptions. Just be sure you use the MAF & MAF sensor from the same series computer. The auto transmission computers use a different start circuit than the manual computers. You can use an auto trans computer in a 5 speed car with no problems or changes. I have done it in my original 89 Mustang GT, and I know it works OK. I would recommend avoiding using a 5 speed computer in an auto trans car due to the possibility of damaging the computer’ internal signal ground circuitry.

The odd duck is the 93 Cobra computer, labeled X3Z which is internally calibrated for 24 lb injectors. Use the MAF & MAF sensor from the X3Z computer to avoid problems with the computer's internal calibration. Try and avoid the 93 Cobra computer if you can.

Some cautions about O2 Sensor harnesses need to be observed to avoid damage to the computer.
Only run a 5 speed trans O2 harness with an A9L. Do not run an Auto O2 sensor harness with an A9L. Doing so will damage the computer’s internal signal ground.
Only run an Auto trans O2 sensor harness with an A9P in a car that has an Auto trans. Using a 5 speed trans O2 sensor harness with an Auto trans will cause no crank problems.
See http://forums.corral.net/forums/general-mustang-tech/1094179-oxygen-sensor- harnesses-manual-auto-differences-year-differences.html for more O2 sensor wiring harness info
If you have a damaged computer with signal ground problems, See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.

All the following are mass air unless they say Speed Density
8LD - MANUAL 88 5.0L Mustang Mass Air - California
8LF - Auto 88 5.0L Mustang Mass Air- California
8LG - Auto 88 5.0L Mustang Mass Air- California
A9L - 89-93 5.0L Mustang 5-spd Mass Air
A3M - 93 5.0L Mustang 5-spd Mass Air
A3M1 - 93 5.0L Mustang 5-spd Mass Air
X3Z - 93 5.0L Cobra 5-spd Mass Air internally calibrated for 24 lb injector
A9P - 89-93 5.0L Mustang Auto Mass Air
A9S - 88 5.0L Mustang California Mass Air
C3W - 89-93 5.0L Mustang Auto
DA1 - 87 5.0L Mustang 5-spd Speed Density
J4J1 - 94-95 5.0L SVT Cobra 5-spd
T4M0 - 94-95 5.0L GT Vert 5-spd
U4P0 - 94-95 5.0L GT Auto
W4H0 - 94-95 5.0L GT
ZA0 - 95 Cobra R
D9S - 88 Lincoln LSC Speed Density



Computer will not go into diagnostic mode on 91-95 model 5.0 Mustangs

Revised Dec 23 2107
1.) To clarify signal ground connections on the engine mounted fuel injector wiring harness and add diagram for the engine mounted fuel injector wiring harness
2.) To add warning about using an automatic transmission O2 sensor wiring harness with a A9L manual shift transmission computer.


How it is supposed to work:
The grey/red wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self-test mode. As long as you are successful dumping the codes by using the gray/red wire on the diagnostic connector for the ground when dumping, the computer’s internal ground on pin 46 is good.

If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1 ohm when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.

Engine mounted fuel injector wiring harness sensors for a 5.0 mustang
63347.gif


What sometimes happens is that the test connector grey/red wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.

OR

If an O2 sensor harness from an automatic transmission Mustang is used with an A9L manual shift transmission computer. The 12 volts from the automatic transmission starter circuit will damage the A9L computer.

The STI (Self Test Input) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.

How to test the wiring :
With the power off, measure the resistance between the computer test ground (grey/red wire) on the self- test connector and battery ground. You should see less than 1 ohm.

attachments\57945


If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the grey/red wire and pin 46 on the computer wiring connector: it should be less than 1 ohm. More than 1 ohm is a wiring problem. If it reads 1 ohm or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1 ohm. More than that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.
While you have the computer connector disconnected from the computer, turn the ignition switch to the Start position and look for 12 volts on pin 46 of the computer wiring harness. If you see 12 volts then you have an automatic transmission O2 sensor harness. That will damage the A9L manual shift transmission computer.


See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self-test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More than 1 ohms is a wiring problem

The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.
eec-iv-computer-connector-for-5-0-mustang-gif.gif


a9x-series-computer-connector-wire-side-view-gif.gif


Diagram courtesy of Tmoss & Stang&2birds

Check out the diagram and notice all the places the grey/red wire goes. Almost every sensor on the engine except the MAF is connected to it.

91-93 5.0 Mustangs
91-93_5.0_EEC_Wiring_Diagram.gif




Complete computer, actuator & sensor wiring diagram for 94-95 Mass Air Mustangs
94-95_5.0_EEC_Wiring_Diagram.gif



See the graphic for the 10 pin connector circuit layout.
salt-pepper-10-pin-connectors-65-jpg.jpg



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
 
Yea ive run trough all of this already, needs a ecu im pretty sure. Just wondering if anyone has had similar symtoms with test light staying illuminated while in test mode but the cluster cel not. I know the bulb is good and it does light in start position. Or actuators and relays clicking like it is going into self test but not flashing just staying lit. Is it possible to have 4cyl auto dash harness incompatibility with the rest of the harness? Seems like eeciv dlc cel circuit isnt connected with the dash cel. Because they have diffrent behaviors. Shouldnt a test light and cel do the same thing while attempting self test.I need a diagram of the cluster and dash harness to chase down check engine light circuit, one i have seems lacking.
 

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Update:
So apparantly there is a power transistor that cycles the STO ground pulses for the MIL through pin 17 If it is bad you will get the conditions i have. It will run well perfect, go into self test, but not flash codes. Definitely an ecu issue. So anyone got one for sale at reasonable price?
 
Did you fry the pin 46 trace on this install? If so, you'll want to test for voltage on pin 46 during key on and key on crank. If you have voltage, you need to correct that issue.

If it's an auto harness, and you are running the manual ECU, my guess is the jumper on the o2 harness is pinned for the automatic. This needs to be corrected if that's the case. It would be the source for frying the ECU's.
 
Did you fry the pin 46 trace on this install? If so, you'll want to test for voltage on pin 46 during key on and key on crank. If you have voltage, you need to correct that issue.

If it's an auto harness, and you are running the manual ECU, my guess is the jumper on the o2 harness is pinned for the automatic. This needs to be corrected if that's the case. It would be the source for frying the ECU's.

No the o2 harness is correct for 93 t5 trace was prob fried before i got it. they grounded sgn rtrn at the eec test connector and it ran ok i saw the jumper and started to investigate found correct o2 harness and no start voltage at 46 harness side so i repaired the trace and removed ground jumper and it ran better but no cel flash so thats when i found out about pin 17 transistor issue. I appreciate the help does anyone here have a lot of knowledge about pcb repair on the a9l/a3m?
 
Update:
Fixed it was a fried pin 17 trace and pin 17 transistor. Used jumpers to fix traces and harvested the transistor form a 302 1990 ford bronco ecu. Not the prettiest but it works im going to clean it up and install it. Check engine light now flashes codes. Transistor was a PNP
20180816_202548.jpg
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