No dash gauges, PCM OBD2 codes, or ignition - JeepForum.com
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post #1 of 10 Old 10-19-2021, 11:44 PM Thread Starter
syncromike
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No dash gauges, PCM OBD2 codes, or ignition

Hello, I recently got a 5.9 and was working through some electrical gremlins, including touching up cold solder joints on VIC, the last one was the "Battery High Voltage" error on the VIC, I went to check field voltage at the alternator and accidentally shorted out the positive wire to ground while engine was running.
The engine immediately stopped, wouldn't start again, gauges on cluster don't work, odometer doesn't light up, and OBD2 Error when trying to read codes. Checked all fuses and relays, all good. Battery is good. 12.6V Engine cranks strong, most other electrical works.
I ruled out all I could besides the PCM so I replaced it with a remanufactured one flashed to my VIN. Same symptoms. I've looked through the FSM, specifically swapped the ASM relay, and getting at my wit's end on this. I've inspected and reseated PCM wiring harnesses and VIC harness as well as inspected. I can't imagine it's the coil or fuel delivery since the gauges don't work and can't read a code.

What else can I do beside replace wiring harness?

Thanks in advance!


'98 ZJ 5.9
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post #2 of 10 Old 10-20-2021, 04:34 AM
jtec
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Details - what MY (model year) is your ZJ?

With KOEO check ASD is there 12v at coil, or injector?

I will ck a diagram with my coffee.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 10 Old 10-20-2021, 08:12 AM
kg6mov
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Details - what MY (model year) is your ZJ?
There’s only one model year of 5.9, 98


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post #4 of 10 Old 10-20-2021, 08:30 AM
zjosh93
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I would get a good wiring diagram. I think there is still a free download of the FSM out there. I only have the 93 version though. Start at the battery and check for 12V all the way to the PCM and ASD relay. If you lose that 12V somewhere, that's the issue. If you get 12V to the PCM then check the grounds. Sounds like a wiring issue.
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post #5 of 10 Old 10-20-2021, 10:12 AM Thread Starter
syncromike
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I have the FSM, not much circuit theory in there on what all is needed to get the PCM to fire up. I can check power at the pins, but from what I can tell searching the forums there are several conditions that will cause it to shut down completely.
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post #6 of 10 Old 10-20-2021, 10:17 AM
jtec
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kg6mov why I ALWAYS ask...
search for 5.9 and ZJ pulls up these manuals , attachment .... IDK
Attached Thumbnails
97.jpg   98 manual.jpg   VIN.jpg  

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #7 of 10 Old 10-20-2021, 01:36 PM
Timo_90xj
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Originally Posted by syncromike View Post
The engine immediately stopped, wouldn't start again, gauges on cluster don't work, odometer doesn't light up, and OBD2 Error when trying to read codes. Checked all fuses and relays, all good. Battery is good. 12.6V Engine cranks strong, most other electrical works.
Which exact wire color in the alternator did you short to ground when engine was running?
Do any of the gauge cluster warning lights come on for a couple seconds when you turn the key to on? Does the VIC work normally?

What you mentioned regarding what is not working is all controlled by the PCM, BCM and partially gauge cluster itself. Data for those is transmitted in the CCD bus.

I tried browsing my '98 FSM wire diagrams for anything common between generator field voltage, and gauge cluster/ PCM/ BCM power feeds. Not exactly easy to find something simple that could cause this.

Are you 100% sure all fuses are good, both in the PDC and in the junction block? Do you have +12V at the injectors, coil, O2 sensor heater feed (DG/OR wires)? Battery voltage at generator field source (DG/ VT wire) with key on engine off?

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post #8 of 10 Old 10-20-2021, 03:44 PM Thread Starter
syncromike
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Quote:
Originally Posted by Timo_90xj View Post
Which exact wire color in the alternator did you short to ground when engine was running?
Do any of the gauge cluster warning lights come on for a couple seconds when you turn the key to on? Does the VIC work normally?

What you mentioned regarding what is not working is all controlled by the PCM, BCM and partially gauge cluster itself. Data for those is transmitted in the CCD bus.

I tried browsing my '98 FSM wire diagrams for anything common between generator field voltage, and gauge cluster/ PCM/ BCM power feeds. Not exactly easy to find something simple that could cause this.

Are you 100% sure all fuses are good, both in the PDC and in the junction block? Do you have +12V at the injectors, coil, O2 sensor heater feed (DG/OR wires)? Battery voltage at generator field source (DG/ VT wire) with key on engine off?
-I shorted the Red field terminal on the alt to chassis ground.
-ABS light comes on for a few seconds, none of the others, VIC functions normal
-100% sure on fuses in both locations, checked them all 3 times now LOL
-no voltage at generator field source with key on, should it though?

I'm checking the 02 Heater sensor and crankshaft position sensor tonight. I'm pretty sure there'd be no voltage to the coil with the PCM not working, so I didn't check yet but will.

I do have an external voltage regulator, but that shouldn't matter since the engine (alternator) isn't running, right?

Thank you!

'98 ZJ 5.9
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post #9 of 10 Old 10-20-2021, 03:53 PM
jtec
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Yes an external regulator (reg) is a BIG difference.

2 wire or 3 wires on reg ?
The power supply/sense at regulator is now where to look.
Its 12v is likely NOT supplied by the PCM. The use of external reg was to eliminate PCM from controlling alternator.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 10 Old 10-31-2021, 05:37 PM Thread Starter
syncromike
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The problem ended up being the socket for fuse 7 under the hood had melted somewhat, fuse 7 did blow but it was replaced.
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'98 ZJ 5.9
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