Power lock problem

[fireball]

I've got a 99 Silverado ecswb and my locks quit working the other day.I have to manually lock/unlock my doors as the door buttons nor the key fob will do it.I checked all the fuses in the circut as listed in my Chiltons manual and did a continuity check with the wiring in the drivers door to the lock solonoid as this is a problem area from what I was told but did'nt find any problems.The lock/unlock relays are clicking and the alarm programs properly its just the lock solonoids are'nt getting any power to them.I see from the wiring schematic that the bcm also controls this function so am I looking at having to replace this or am I missing something?Thanks.

[GM-Tech]

It's not the BCM. While the locks can be operated by the BCM, such as when you use the remote, when you press the lock button on the door you are directly activating a relay. The BCM doesn't play into it at that point.

 

If the relays are clicking when you do this, the switch is getting the signal to the relay. Whether or not anything is going through the relay contacts is something you'd have to test. And if it is, is it actually getting to the lock actuator.

[fireball]

Where should I check next?I'm not sure of what to look for that would cause both door lock to fail at once.As you stated there may not be any power getting through the relays so is there as proper procedure for testing these?Thanks.

[GM-Tech]

There are two separate fuses for the locks. Have you checked those? There's a MIR/LOCK fuse and a DR LOCK fuse in the left fuse block. The MIR/LOCK fuse is for operation of the relays. The DR LOCK fuse is what actually supplies power to the actuators, through the relays. I would assume since you can hear the relays click, the MIR/LOCK fuse is okay.

[fireball]

I have checked every fuse listed in the schematic and they all look ok so other than replacing the fuses with new ones just to rule out them I'll have to keep working at the problem when I get some free time.