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2002 gmc envoy_slt_xl
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100 Posts
Discussion Starter · #1 ·
For the last 4 days when you have all the doors locked and you want to unlock all the doors with either the key fob by double clicking or using the unlock button on the front doors. The 2 rear doors remain locked. The front doors and rear hatch open. You have to reach throgh behind each seat and manually unlock each rear door.
You can hit lock all doors and they all lock, but the 2 rear doors wont unlock again. So you must manually unlock the 2 rear doors again.
Also the same thing when using the remote starter.

Any ideas where to look for the problem, because I have run out of my few ideas. I dont know where fuses or relays are for the rear doors, so no I haven't checked them.
Thanks for any help.
 

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2004 gmc
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26,181 Posts
Fuse #21 in the rear fuse block runs lock and unlock functions, so we know that's OK. Relay #24 is the unlock relay for rear doors only, and #18 is the lock relay. Since they're labeled LOCK and UNLOCK in the Owner's Manual, but don't mention they're for the rear doors only, it's understandable that you didn't think to just interchange them.

Anyway, just interchange them to confirm that it's the relay and not the wiring.
 

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2002 gmc envoy_slt_xl
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100 Posts
Discussion Starter · #5 ·
Child safety locks are in the open position :raspberry.

Fuse is good, lock relay clicks when locked, unlock relay didn't make any sound, so I switched relay positions and the same thing happened. So its not the relays either :thumbsup:.

next troubleshooting area to check? :thx
 

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2004 gmc
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26,181 Posts
The unlock signal comes from the BCM (connector C3, pin A5) to the relay coil, whose other side goes to 12V. Getting a meter on the relay fuse block socket or the BCM pin is the next step, to see where the signal is going missing. It may also be a bad BCM.

Are you into electrical troubleshooting, experience and tool-wise?

I have a backlog of schematics to scan in to help other folks, so I could add this to the list if you're up for it. Otherwise, you need an electrically-qualified mechanic with access to trailvoy schematics.
 
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