Fuse number 2 PCM blows

Tiny
JOEGO
  • MEMBER
  • 1995 JEEP GRAND CHEROKEE
  • 5.2L
  • V8
  • 4WD
  • AUTOMATIC
  • 220,000 MILES
Fuse number 2 (PCM) blew intermittently for a few days causing engine shutdown, now it blows immediately on replacement. Removed ASD relay still blows. With the PCM Disconnected the PCM fuse does not blow, load side of fuse resistance open. Resistance on load side of fuses is .2 ohms with PCM connected.
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Monday, September 7th, 2020 AT 2:07 PM

6 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good evening,

If the fuse fails with the PCM disconnected, then the PCM is internally shorted out. It must be replaced.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-a-car-fuse

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

I attached the diagram for you. The PCM is the only thing the fuse controls.

Roy
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Monday, September 7th, 2020 AT 3:11 PM
Tiny
JOEGO
  • MEMBER
No, the fuse does not fail with the PCM disconnected.
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Monday, September 7th, 2020 AT 3:54 PM
Tiny
JOEGO
  • MEMBER
Have visually inspected all engine and under-hood wiring, no faults found. Also did a shake test on wiring with a latching continuity tester again no faults found. Maybe I need a new PCM, just would like to know how the PCM divides the voltage from the number 2 fuse before shotgunning parts.
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Monday, September 7th, 2020 AT 4:08 PM
Tiny
ASEMASTER6371
  • EXPERT
That fact that the fuse does not fail means the ECM is the issue and must be replaced.

The reason is internal and special equipment is required to find the failure.

Roy
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Monday, September 7th, 2020 AT 4:13 PM
Tiny
JOEGO
  • MEMBER
I Agree it could be a PCM internal fault, but I doubt it because the fuse blew intermittently at first. I think it could also mean a component down line of the PCM faulty. I would like to trouble shoot further before buying an expensive PCM. Replaced PCM fuse still blows.
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Wednesday, September 9th, 2020 AT 5:59 PM
Tiny
ASEMASTER6371
  • EXPERT
If you disconnected the ECM and the fuse did not fail, that eliminates all the wiring up to the ECM.

Did you use a new or used ECM?

Roy
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Thursday, September 10th, 2020 AT 3:47 AM

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