Rear Door Locks Not Working

[brickford5]

Like the title says, my rear door locks are currently not working. Front door locks work fine but using the remote or the lock button on driver door make no difference on the rear locks.

The truck is newer to me so I don't know a lot of it's history but it does look like it had a security system at one point (column was punched and radio missing when I got it, so I replaced both of those).

Here is what I have done so far:

• Tried a new door lock actuator (no V seems to reach the actuator for either back door even though both all relays/fuses are good)
• Can hear both 'Lock' and 'Unlock' relays at the drivers side fuse box. Still swapped with new ones.
• I can remove both relays and the '20A Lock Fuse' and front locks still work (removing the 10A PDM does kill the front locks)

I'm kind of stumped here and moderately dumb when it comes to electrical troubleshooting. Any pointers would be appreciated!

 

[brickford5]

Attached is a pic of my fuse box. Is it weird that my front locks both lock/unlock without any problem with all the circled removed except the 10A PDM? (So without the Lock/Unlock relays and the 20A Locks fuse)

 

[DURAMXD]

I had a Yukon that did the same thing. I fought it forever. Intermittent rear lock issues. Sometimes they worked, sometimes they didn't, sometimes it was the FOB, sometimes from the door switch. I could swap/pull both relays and the fronts would always work but not the rear. Sometimes swapping the relays would make the rear ones work for a couple cycles and then stop again. After chasing everything I could think of I just put in two different relays and they always worked after that. Might be worth a shot if you have another vehicle to swap them with around.

 

[brickford5]

Thanks for the input DURAMXD. I did replace both relays and had no changes. The rear doors never work unfortunately. May need to start chasing wires...

 

[serioustones]

It could be the wires.