Electrical issues with 97 Jeep TJ 2.5 5-speed

[Taylorpolk34]

I am at an absolute loss with my 97 tj. I have replaced the wiring harness with a good used harness from eBay (every pigtail connector on the old harness had exposed wiring)

The jeep ran good until the alternator failed. I replaced the alternator and then the gauge began to jump to 19 volts. I took the jeep to a local mechanic who suggested I install an external voltage regulator to which I agreed.

Once the external regulator was installed the gauge began to read perfect at 14.2 volts and then suddenly drop to zero. I tested the voltage at the battery and it was holding strong at 14.2 which lead me to believe I had a bad ground. Killed the jeep, cleaned all grounds and went to start the jeep to see if it had resolved the issues. Crank, no start. Bad PCM, confirmed by physical inspection revealing a hole burned through the PCM.

Purchased and installed new PCM and the jeep fires up and starts but now I have no fuel or oil pressure gauges and the voltage is once again jumping to 19 volts on the dash gauge but reading a steady 14.2 on the battery.

Could this possibly be a faulty PCM?

 

[macleanflood]

@Wranglerfix

www.wranglerfix.com

Send your PCM to Mark for testing.

While you wait a couple of days take apart the new harness and verify everything.

-Mac

 

[Wranglerfix]

I am at an absolute loss with my 97 tj. I have replaced the wiring harness with a good used harness from eBay (every pigtail connector on the old harness had exposed wiring)

The jeep ran good until the alternator failed. I replaced the alternator and then the gauge began to jump to 19 volts. I took the jeep to a local mechanic who suggested I install an external voltage regulator to which I agreed.

Once the external regulator was installed the gauge began to read perfect at 14.2 volts and then suddenly drop to zero. I tested the voltage at the battery and it was holding strong at 14.2 which lead me to believe I had a bad ground. Killed the jeep, cleaned all grounds and went to start the jeep to see if it had resolved the issues. Crank, no start. Bad PCM, confirmed by physical inspection revealing a hole burned through the PCM.

Purchased and installed new PCM and the jeep fires up and starts but now I have no fuel or oil pressure gauges and the voltage is once again jumping to 19 volts on the dash gauge but reading a steady 14.2 on the battery.

Could this possibly be a faulty PCM?

We can get you a pcm as quickly as tomorrow. You can call me to discuss in further detail if you'd like.

Thanks,

Mark

 

[Taylorpolk34]

We can get you a pcm as quickly as tomorrow. You can call me to discuss in further detail if you'd like.

Thanks,

Mark

I reinstalled my old PCM to see if at least the gauges would work so that I could eliminate an issue with the fuel pump or oil pressure gauge and to my surprise all gauges work and the jeep started right up. I’m leaning towards some kind of short or bad ground. What puzzles me is there is a literal hole burned into my old pcm and all the sudden it’s working without issue.

 

[Cooper Smith]

I reinstalled my old PCM to see if at least the gauges would work so that I could eliminate an issue with the fuel pump or oil pressure gauge and to my surprise all gauges work and the jeep started right up. I’m leaning towards some kind of short or bad ground. What puzzles me is there is a literal hole burned into my old pcm and all the sudden it’s working without issue.

Uh, can we get a photo of said hole?

 

[Taylorpolk34]

Uh, can we get a photo of said hole?

 

[Cooper Smith]

View attachment 648897

Yeah, you need a PCM. That burned right through the traces of the board.

 

[Taylorpolk34]

Yeah, you need a PCM. That burned right through the traces of the board.

Purchased and installed a new pcm but my gauges aren’t responding. The old pcm with the burn is working with no issues. Makes no sense to me.

 

[Taylorpolk34]

Purchased and installed a new pcm but my gauges aren’t responding. The old pcm with the burn is working with no issues. Makes no sense to

Purchased and installed a new pcm but my gauges aren’t responding. The old pcm with the burn is working with no issues. Makes no sense to me.

“An open or shorted condition detected in the auto shutdown relay circuit. An open condition detected in the ASD relay output circuit. An open or shorted condition detected in the fuel pump relay control circuit. An open circuit between PCM and fuel gauge sending unit. Circuit shorted to voltage between PCM and fuel gauge sending unit. No movement of fuel level sender detected.”

That’s the code I’m getting with the brand new PCM installed just for extra context.

 

[macleanflood]

Where'd you source the PCM?

-Mac

 

[Taylorpolk34]

Where'd you source the PCM?

-Mac

Mechanic pointed me towards flagship one. 363 bucks for a plug and play sounded too good to be true and I’m seeing why now.

 

[Obi-Wan]

Mechanic pointed me towards flagship one. 363 bucks for a plug and play sounded too good to be true and I’m seeing why now.

Mark @Wranglerfix is the only source of quality PCM's and service for our TJ's. Period.

 

[Chris]

Mechanic pointed me towards flagship one. 363 bucks for a plug and play sounded too good to be true and I’m seeing why now.

Damn, you screwed up with FS1, that's for sure.

We avoid them like the plague around here.

 

[Taylorpolk34]

Damn, you screwed up with FS1, that's for sure.

We avoid them like the plague around here.

This is my first jeep and I’ve only had it about 3 months, I really should’ve checked this forum before ordering off of FS1. It’s been a learning experience for sure.

 

[Terry D]

I am at an absolute loss with my 97 tj. I have replaced the wiring harness with a good used harness from eBay (every pigtail connector on the old harness had exposed wiring)

The jeep ran good until the alternator failed. I replaced the alternator and then the gauge began to jump to 19 volts. I took the jeep to a local mechanic who suggested I install an external voltage regulator to which I agreed.

Once the external regulator was installed the gauge began to read perfect at 14.2 volts and then suddenly drop to zero. I tested the voltage at the battery and it was holding strong at 14.2 which lead me to believe I had a bad ground. Killed the jeep, cleaned all grounds and went to start the jeep to see if it had resolved the issues. Crank, no start. Bad PCM, confirmed by physical inspection revealing a hole burned through the PCM.

Purchased and installed new PCM and the jeep fires up and starts but now I have no fuel or oil pressure gauges and the voltage is once again jumping to 19 volts on the dash gauge but reading a steady 14.2 on the battery.

Could this possibly be a faulty PCM?

I had the same problem and the problem I had with the new ecu was it was programmed for a chipped key and my jeep was not set up for a chipped key, I returned to the company who I had bought it from and the found that they programmed it for a chipped key so they reprogrammed it and has been great.