Recently purchased 2008 Tahoe with 130K miles. Working thru some quirks, one of which is none of the power door locks work. Key fob might also be a problem, but for now I'm just trying to use the switch on drivers door. When I press the switch I can hear a relay clicking under the dash, above the drivers left leg, but none of the locks engage. My 1'st guess is the individual actuators in each of the doors, but find it hard to believe that all 4 are toast. I've previously owned 96 and 99 Tahoes, both purchased used and driven to the end of their usable lives. Never had an issue with power locks on either of those two vehicles. Aftermarket replacement actuators available, but before I buy the 1'st one as a trial I thought I'd seek expert advise.

 

Check the fuses in the instrument panel fuse block (UNLCK1, UNLCK2, LCK1, LCK2), the relay you hear clicking sends power to these fuses for the back/rear doors.
The front doors are controlled by the door modules (switches) and fuses DDM, PDM
The FOB receiver is fuse DSM
Use a meter to test the fuses for conductivity, just looking at them isn't reliable.

 

Thanks much a55bruce. I had already visually checked the LCK/UNLCK 1&2 fuses. Per your suggestion went back and did a continuity test on those four and also checked the DDM & PDM fuses - that I was not aware of before your reply. All is well with the door switch, relay (it clicks) and fuse box box so going to try swapping out actuators (back doors 1'st). Aftermarket parts avail for 25% of OEM so not a very expensive debug step. Thanks again

 

I'd put a volt meter or test light across the actuators first. Check for power when clicking the locks. Don't measure to ground, measure across the wires going to the actuators. The lock/unlock is done by reversing the polarity to the actuators.
Why waste time & money on swapping actuators if power is not getting to the doors.

 

Update - installed after market lock actuator replacements (Amazon purchase) in both rear doors yesterday and now have working rear door power locks. Ordered a pair for the front doors. A few more fixes and modifications (e.g. front hitch receiver) and she'll be ready to hit the beach for the surf casting season. Hands down Tahoes are the best beach buggies on the planet - this is my 3'rd.