Another PCM diagnostic question

alabamayj

alabamayj

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Joined
Aug 17, 2024
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2
Location
Prattville AL
Proud new owner of a 1993 YJ 2.5L with a 5 speed. The Jeep is in pretty good shape mechanically, it seems. However, the previous owner ran into a no-start issue and tore open all of the wire looms looking for the issue. I have a feeling that it is the PCM. I first replaced the three capacitors on the board. However, I still have no engine warning light, etc. showing on the dash. It is completely dark. I thought maybe there was a disconnect between the harnesses and the gauge cluster. However, I don't think that there is. As of now, turning the ignition switch on does not trigger the fuel pump relay either. I have power and good fuses in the relay junction box and in the fuse block on the firewall.

My question is concerning the PCM. I am seeing power coming into it. However, pin 32 (engine malfunction light) does not have any voltage coming out when the key is turned on. If the PCM were working correctly, should it have voltage coming out of pin 32? I think this is the one that lights the light on the dash, from what I can tell on the wiring diagrams. Any thoughts?

Thanks!
 
alabamayj said:
Proud new owner of a 1993 YJ 2.5L with a 5 speed. The Jeep is in pretty good shape mechanically, it seems. However, the previous owner ran into a no-start issue and tore open all of the wire looms looking for the issue. I have a feeling that it is the PCM. I first replaced the three capacitors on the board. However, I still have no engine warning light, etc. showing on the dash. It is completely dark. I thought maybe there was a disconnect between the harnesses and the gauge cluster. However, I don't think that there is. As of now, turning the ignition switch on does not trigger the fuel pump relay either. I have power and good fuses in the relay junction box and in the fuse block on the firewall.

My question is concerning the PCM. I am seeing power coming into it. However, pin 32 (engine malfunction light) does not have any voltage coming out when the key is turned on. If the PCM were working correctly, should it have voltage coming out of pin 32? I think this is the one that lights the light on the dash, from what I can tell on the wiring diagrams. Any thoughts?

Thanks!
Click to expand...

Hi, you say you replaced the 3 capacitors on the ECU? Can you tell me what 3 capacitors you replaced and what were the replacement values / numbers of the new ones you out in. My Jeep is at its third mechanic and although we fixed the fuel issue, we now have no spark to the injector. Apparently the ecu again. I have bought three in 8 months and cant afford another one so i was going to pull my first one and solder new caps in to see if it fires up again. Thanks!
 
jpjeep26uk said:
Hi, you say you replaced the 3 capacitors on the ECU? Can you tell me what 3 capacitors you replaced and what were the replacement values / numbers of the new ones you out in. My Jeep is at its third mechanic and although we fixed the fuel issue, we now have no spark to the injector. Apparently the ecu again. I have bought three in 8 months and cant afford another one so i was going to pull my first one and solder new caps in to see if it fires up again. Thanks!
Click to expand...

The originals and replacements were all 25V 220 uf. Thanks
 
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