Not exactly sure what you were doing, with a continuity light, or even jumping the circuit.....all you are doing is creating a signal to the to the door switch assembly.....you have no idea if the the switch assembly is sending a Class II signal to the DDM.....

I pulled the switch harness off the lock switch. I bypassed the lock switch by jumping the wires in the harness connector to activate the actuator - thinking if there was power to that point the actuators would function - they didn't, so I'm assuming there is no power through that harness to the lock switch itself (which is probably ok).

Now I'm trying to see if the power interruption is caused by a bad wire in the door harness somewhere - leading into the door to the DDM at the jamb, or from the DDM out.

This just feels like a new DDM is coming my way and I'm gonna hate shelling out the bucks for my dealer to install and program. Who knows, I might get lucky and find a lose connector at the DDM from a previous repair. That would be a nice Xmas present.

I am a little confused......were you using a continuity light or a test light...to me, a continuity light is self powered...

Thank you,

This is a test light with an alligator clip on one end of the wire, and a pointed probe on the other - which contains a small lamp that resembles an automotive glass fuse. It is not self-powered. The lamp did not light in any of the jumped combinations I mentioned earlier. The test light has a test voltage rating of 6v minimum.

I also jumped the harness terminals with a metal paper clip - just to be sure there was a connection made.

When the actuators did not work during my jump (bypassing the lock switch), I figured there was no power at the terminals in the harness connector.

Here'* a pic of one nearly identical to mine - unpowered - internal bulb shaped like glass auto fuse

Are there other components inside the door lock switch besides simple contacts?

That lamp will not light because if you look at the wiring diagram there is a built in sensing resistor in that circuit...that resistor is a lot higher than your lamp, so when you complete the circuit through your test light to ground, all the voltage will drop across the sensing resistor, and not enough across your lamp bulb, thus it will not light....

Ahh.. ok. Good to know. How about when I jumped the terminals with a metal paper clip? Same problem?

When you jumpered with the pin, the actuator didn't work.......everything works on Class II serial data(nothing is hardwired directly)...did the switch assembly send a Class II signal to the DDM? Did the DDM receive it? Did the DDM then activated the actuator? Instead of a test light, you should have used a voltmeter......you would have read 12 volts on each line....then when you pressed lock or unlock, each respective line would have gone to zero.....if it did, all that would prove is that the Driver'* door lock switch is working....it doesn't tell you if the DDSA is sending a serail data signal to the DDM....

Basically, what they have done is try to build a better mousetrap....without a scan tool to see if Class II data is being sent or received, you are just guessing what is wrong....

Thanks for the detailed explanation. I thought I may have been dealing with measureable voltages. Even using a voltmeter would not help in this situation, as It appears the switch is not the problem (because, I assume, all switches went out at the same time - except for mirrors that went earlier).

Is an OBD Scan Tool required?

I'm pretty much resolved to the fact this is going to involve replacement/programming of a new DDM - so a requirement for OBD scanning is out of the question for my troubleshooting attempts. Dealer wins.

No, a normal OBD scantool will not work in this case.

You need access to a Tech2 tool. Its a super duper OBD diagnostic tool that GM dealers use to program and diagnose GM vehicles. They can use it to individually test all modules in a vehicle and can tell if they are talking to each other via the data line.