Dash Lights Going Crazy then Limp Mode

[hcpcjj]

I'm moving this from a previous TPMS discussion. I am at a loss. Started it this evening. Started right up. 30 seconds later, every possible warning light, lost power steering, wipers came on, headlights came on. Engine cooling fan turned on. Wouldn't go into drive. Wouldn't turn off. Had to disconnect the alternator & positive cable to shut it down. Had a new CAN bus connector that I carry as a spare. Put that in, no change. It starts up and after 10 seconds, same thing. Starts with ABS, then goes on to traction control, then spirals from there. AUX battery is bypassed and has been for the past few weeks with no issues. I reconnected the AUX battery & reinstalled the fuse. Same thing. Also has a brand new main battery. I put the charger on it all night. Charger reports full charge & Jeep starts no problem. Took the battery back to Autozone for load test & shows no issue. I can post a video if you think it will help.

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[Stan B]

I read through your TPMS thread, and the remote start one you started before that. Sounds like you have some electrical gremlins. Maybe a bad ground connection.

If you have a code reader that can access all modules, does it have any stored codes?

Do you have a multimeter? Check resistance between the battery negative terminal and something metal on the engine block. Not as good as a voltage drop test, but somewhere to start.

 

[Bob Burd]

Could be a bad ground as mentioned. You can find the wiring diagrams on the Electrical,etc forum. One of those shows all the grounds that you can check.

Could be overloaded canbus, too. Do you have any aftermarket devices on the bus, like a Tazer or RPM fan controller?

 

[hcpcjj]

No aftermarket devices. I'll check the grounds this weekend.

 

[LargeSarge]

Had a similar issue with my pre-Jeep vehicle (Mini Cooper); ended up being a faulty alternator causing overvoltage. Symptoms got worse over a two week period. Started with the audio system cutting out then phantom warnings (hood open, tpms etc) and finally limp mode. Replaced the batteries, then the main ground wire, finally the alternator, which solved it. Traded it in for my JL the next week.

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