Ok, looking for some help here. I recently bought a 2000 Blazer LT (4door). The power door locks will not work from either door but will work by remote fob. Also, the power mirrors won’t work and the rear glass will not unlock (from push switch on dash or from switch on tailgate). I checked power to the rear glass lock actuator and had power. With a test light on the connector I can push the button on the tail gate and it lights up. Good power there so I replaced the actuator but still nothing. Also checked power to power door lock switch on drivers door and had power at the switch. Had power to the mirror switch so I replaced it, but no change. I’m confused! I checked all the fuses and they seem fine. What am I missing here?

 

The locking and unlocking process is not as simple as providing a single power and ground to the motor. A set of relays has to swap power and ground to get the motor to go in opposite directions. So checking the locking/unlocking motor power feeds would require looking for power on one wire and ground on the other wire during a call for lock and then the opposite with a call for unlock. The remote key FOB receiver and associated BCM, switches and swapping relays all use different power sources. So. your problems can be power, fuses, relays, switches, wires or connectors. Lets start with fuses, check:

TRC fuse 10A, UH fuse block (this one should be good)
PWR Locks Fuse 14, 15A IP fuse block
Mir/Lock fuse 7 3A UHFB

We will go from there, if you are up for a systematic analysis and identification of the problem. I'm not a "parts cannon" guy as Swartlink calls it, but we can fix your problem.

George

 

Look for a 3amp fuse under the hood. I forget what name it goes by, but you should be able to find it pretty easy. Pull it out and take a look, pretty sure you will find it bad.

 

Ever figure this one out?