Possessed Power Door Locks on '90 Burb

[BigDick]

My power door locks on my '90 Burb are possessed. They will lock anytime unpredictably. If I get out of the Burb while it's idling in Park, it sometimes LOCKS and if I don't have an extra key.... well. I have learned to leave the window open. It will sometimes lock them with the engine off, and I exit the vehicle with the keys in the ignition. I've threatened to buy a Toyota, but it keeps doing it to me. What triggers that relay, and where is it?

 

[gmbellew]

I think the relay is by the fuse panel. does it ever do weird things when you use the windows? I had a strange issue one time with locks and windows and it was a mouse chewed harness under the dash. that's the only place the harness for those two things runs together.

is there any aftermarket keyless system remnants in the wiring?

otherwise I'd be looking at the switches for some wires touching that shouldn't be.

and it does it just sitting there? that's a strange one.....

 

[Snoots]

Step 1: Get a spare key cut.
Step 2: Remove you door panel and start moving wires around. You likely have an issue where the harness passes thru the A pillar.

 

[BigDick]

This never has occurred when actuating the power windows. It occurs as stated. I have not pulled the master lock switch to examine, but that is a good thought.

 

[BigDick]

i looked on ebay for a wiring diagram. But who said Jesse James was dead? Some sources are reasonable but have outrageous "shipping charges" even though they can be downloaded.

 

[gmbellew]

the GM wiring diagrams, along with owners manuals, repair manuals, and service manuals, are in the reference library of this site

 

[BigDick]

Being a new member I did not know that. Thank you

Okay. The schematic is page A-136. I am a retired controls tech that has worked and written schematics all my working career, and I have to say that automotive schematics suck the big one! Clarity and intuition know no place in them. I also forgot that my 90 Burb has a factory Keyless door system but, since its been sitting for 20 years I forgot it had that and the fob would need batteries. It is possible that black box is the culprit but I cannot find anything about it.

On that schematic, there is no reference on the door switch that initiates the door lock when the shift lever is placed in drive. Nor, is there any reference to a keyless entry system that my Burb has. OEM option? And I cannot find any reference to either on the LMC site. Any suggestions are welcome.

 

[Snoots]

automotive schematics suck the big one!

Amen to that!

 

[Snoots]

door switch that initiates the door lock when the shift lever is placed in drive

This is controlled by the BCM.

 

[gmbellew]

Being a new member I did not know that. Thank you

Okay. The schematic is page A-136. I am a retired controls tech that has worked and written schematics all my working career, and I have to say that automotive schematics suck the big one! Clarity and intuition know no place in them. I also forgot that my 90 Burb has a factory Keyless door system but, since its been sitting for 20 years I forgot it had that and the fob would need batteries. It is possible that black box is the culprit but I cannot find anything about it.

On that schematic, there is no reference on the door switch that initiates the door lock when the shift lever is placed in drive. Nor, is there any reference to a keyless entry system that my Burb has. OEM option? And I cannot find any reference to either on the LMC site. Any suggestions are welcome.

keyless system is only aftermarket. likely that is the cause of your issues. I'd recommend removing it and replacing with a new aftermarket system.