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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6531
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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Mustang: I put a new ecu in my 91 mustang and cant read codes

Customer Question

I put a new ecu in my 91 mustang and cant read codes bought two different code readers
Submitted: 1 year ago.
Category: Ford
Expert:  A. Penland replied 1 year ago.
Does the engine start? Does the check engine light come on?
Customer: replied 1 year ago.
Engine starts and has check engine tried the jumper and test light procedure to the light stays on solid doing the koeo test
Customer: replied 1 year ago.
Tried two scan tools they start the self test I hear clicking and pump turn on but light stays solid on code reader
Expert:  A. Penland replied 1 year ago.
Is this the same problem you had with the original PCM you removed?
Customer: replied 1 year ago.
No first ecm stopped working after years of working sent in for a a1 Cardone replacement
Expert:  A. Penland replied 1 year ago.
Read the steps below and see if you can get codes.You may have a problem with the PCM you just installed.
Customer: replied 1 year ago.
Voltage and test light stay on constant from selft test pin to positive
Customer: replied 1 year ago.
Bad remanufactured ecm only thing I can think
Expert:  A. Penland replied 1 year ago.
It looks like that to me also. It is rare to get a bad PCM from A1 Cardone. They are pretty good at rebuilding them.
Customer: replied 1 year ago.
Guess ill give them a call
Expert:  A. Penland replied 1 year ago.
The light should flash during the self test.
Customer: replied 1 year ago.
Ya I did test on my 91 truck to make sure I'm doing it right and it started working right away
Expert:  A. Penland replied 1 year ago.
Ley me look something up first. What engine does it have?
Customer: replied 1 year ago.
5.0 aod transmission
Expert:  A. Penland replied 1 year ago.
Lets check the wiring between the PCM and the self test connector. Get an digital multimeter and set it to ***** disconnect the battery and disconnect the PCM. Below is pin out of the self test connector and the PCM.Check the resistance between the pins below.PCM 22 LB/O ...SELF TEST CONNECTOR 926PCM 17 PK/LG ...SELF TEST CONNECTOR 658PCM 48 W/P ...SELF TEST CONNECTOR 209PCM 46 GY/R ...SELF TEST CONNECTOR 359
Customer: replied 1 year ago.
Between both commectors on ones asked about I read closed shorted
Expert:  A. Penland replied 1 year ago.
Closed shorted? With the meter on OHMS, you should get 0.0 OHMS on each wire.
Customer: replied 1 year ago.
Sorry im a journeyman electrician thats what we call 0.0 ohms when checking continuity. Yes 0 ohms
Expert:  A. Penland replied 1 year ago.
No problem. The automotive industry we call it continuity. With the wiring good, the problem is the PCM.
Customer: replied 1 year ago.
OK thanks ill try a new pcm
Expert:  A. Penland replied 1 year ago.
Your welcome, Thank you.