I recently purchased a 96 Jimmy. I am having some electrical problems.

1) rear hatch opens when the drivers door is unlocked using either the door switch or the remote. Note: the door must be locked and then unlocked. Pushing the unlock button while the vehicle is already unlocked does not cause the hatch to trigger.
2) rear hatch opens when shifted into drive or park.
3) power drivers seat controls do not work
4) radio is erratic. no control with both the *****, but all other controls work. Radio chooses by itself to change volume, power on/off. Radio display will sometimes blink and change on its own.
5) Rear Wiper does not work

Where do I start the diagnostics? Relays? grounds?

Updates:

Be sure to read the whole thread!

Power seats now work. The wire connections under the carpet had failed. I spliced in new wire and now have power to the seats.

The rear hatch seems to work now. Maybe it was a victim of the power and ground wire that I spliced to fix the power seats or possibly I moved a loose connection and inadvertently hid the problem for now. [The problem was both electrical and mechanical. Fixing the wiring splices and lubricating the rear hatch button solved the problem]

Rear wiper motor replaced and switch cleaned and reassembled. Wiper works, but the motor seems to catch sometimes on the return swing of the arm. The motor does not appear to be running when it catches. Possibly there is still a wiring problem with the wipers. [The battery was just run down from working on the car with the doors open. The wiper is very sensitive to low voltage]. Wiper washer fluid leaks from the rear wiper arm when the rear gate is down. [Fixed by replacing the check valve in the fluid line near the tailgate. It was frozen in the open position]

I still have no idea how to diagnose the radio problem. [I finally swapped it into another vehicle, definitely a radio problem]

 

WOW, sounds like some sort of grounding issue & wires pinched together/grounding each other to activate things. I'm not sure on your vehicle but the tedious task of hunting electrical demons is upon you.
I'd try to think of common things, where the wires for this would run & how they could be effected. Like the hatch & putting it into drive or using the remote... thats odd, but the wires or mechanical for the shift - what wires are around that? Something/s seem to be sending a groundloop perhaps?

Sorry, just thinking outloud, hope it helps.
Good Luck!

 

Some updates are included in the initial post. I am still trying to figure out how to diagnose the radio problem. Anyone havce an idea where to start?

 

Bump: Does anyone have wiring diagrams for the stereo system in a 1996 blazer or a diagnostic procedure to check the radio?

 

Okay. I found some wiring diagrams online for my '96 and purchased a subscription to AlldataDIY.com which is helpful for connector and splice locations.

I've nearly isolated another wiring problem. Moving the wiring bundles under the carpet behind the back seats there is a short on the white (switch) wire for the door lock system. Sometimes it is shorted to power (org) and sometimes to ground. I'll track it down this weekend.

For the sake of completeness I'll add more background. When I purchased the vehicle a few weeks ago the 3/4 clutch pack was gone in the tranny and a code was set for a bad TPS voltage. I saw that no one had ever performed the wire harness mod for the bad ECM ground in the 96 ecm. I updated the harness and swapped in a rebuilt tranny that I had in the garage. The harness repair fixed the TPS voltage (bad reference ground) and the new tranny shifts fine.

 

The white wires in the door lock/ interior light circuit have two splices under the rear seat on the drivers side. I re-wrapped these and seem to be back in business.

The radio failure seems to be inside the radio. I am on the search for a new radio now.

 

Sorry to reserect a dead thread but, this one is the only reference the search found. Could you please point me to where you found the harness mod instructions or tell me what you did. I don't believe this has been done on my 96 and would like to do while I'm tracing grounds down this weekend. If this has anything to do with the big three I'm covered though.

Thanks,
Don

 

The splices for the power seat are under the carpet between the pedals and the front seat. You will need to remove the seat, pull back the carpet and open the plastic wire tray. Split open the tape on the wire bundle and you will find the splices.

The splices for the power windows is in the same wire tray, but further back. I think they were in front of the rear seat (but might have been under the rear seat) I had the seat out at the time I as doing the repair.

I also found that the rear door hatch push button will stick sometimes. Clean and lube it too.

 

Thanks for the relpy Kevin. I should have been a little more clear though. I meant the mod you refered to with the ecm ground. Is it soldering new wire into the harness and grounding to frame by chance?

 

The harness update to fix the ecm ground problem is covered by TSB 667103. A google search will pull up the instructions.