Final Update:
I replaced the two relays in the door module and everything works perfectly now.

If I were going to do this over, I would first do the pin jumping and voltage checks shown in post #6. That would have proven that there was good power and ground (so door jamb connector is good) and that the lock actuator was functioning. With those two things known, the door module is the only possible culprit left.

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Hi all. I just bought a gorgeous 2001 C5 off of Bring a Trailer. I was middle man for my longest time buddy as it was local to me but 1200 miles from him.

As always happens with a used car, when I got it home, the first problem popped up.
The drivers side door locks don't work with the key fob or the door button.
Thanks to Corvette Forum and YouTube, it seems like the most popular fix involves replacing the relays on the Door Lock Module.
Also mentioned are flaws in the connectors in the door jamb or the themselves.

Here's my diagnostic observations so far...
Passenger side seems to work normally - both with the fob or either interior panel switch.
Driver's side will not LOCK or UNLOCK with either the fob or either door panel button.
If I put my hand on the interior door panel and work the switch I can feel a clicking both lock and unlock where the door lock module lives.

My conclusions...
If the problem is in the module, the fact that both lock and unlock don't work would have to mean that both module relays are bad. It is unlikely that both module relays would be bad on this 35k mile car.
The fact that all the switches on the drivers interior panel except the driver's side lock switches work says the grounds and power wires are functioning. The clicking in the module area indicates that the relays are actuating (if not actually making contact...).
The failure that would fit these conclusions is in the driver's side door lock actuator.
Soooooo, my next step is to dig down to where the door lock actuator lives, disconnect the wires and hot wire it to see if it responds. If not, replace it.

What do all you experts think of all this? (I have about seven hours of C5 experience at this point...)

 

Unfortunately we won’t be able to run you step by step on how to diagnose your door locks but here is the wiring schematic…hope it helps.

 

Thanks.

The car came complete with a full set of GM manals (score).

The capture you show above is soooo easier to read than the B/W printed diagram. Just a little color coding makes it much easier for your brain to follow.

 

You can subscribe to Alldata DIY and get these OEM and color redrawn schematics where you can highlight each of the wires for $19.99 for a month.

 

Ok, I got some follow on info.

I unplugged the connectors at the door lock actuator.

I hooked a voltmeter up to the two terminals of the actuator motor wire plug and I get a flash reading of something like 4.4 volts when I operate the interior lock switch. By "flash reading" I mean the digital meter shows the +/- 4.4v for about a quarter second then goes back to zero. Positive one way and negative if button pushed the other way.

I removed the lock actuator and tested it on my bench by connecting 12v across the two motor drive terminals. I found that the actuator seems to work correctly both lock and unlock.

Hmmmmm. IIRC, the manual says that the door module should send a signal to the actuator motor for five seconds. I'm getting just a flash and well less than five seconds. Plus, the voltage is only in the 4v range (I kind of expected 12v).

I'm coming to the conclusion that the fault is in the door module after all. Anyone care to weigh in?

Does anyone have experience with Autoclockrepair rebuild service on eBay?

 

OK, so I re-installed the lock actuator assy and started doing some testing on the circuits.

I removed the connectors from the door module and checked the voltage between the larger gauge black (C2-C) and orange (C3-A) wires which showed battery voltage as they should. This tells me that there is power to the door module.

Next I applied a jumper between C3-A and C3-D plus C2-B and C2-C. Viola, lock actuator works perfectly. I didn't bother to check the lock function as it worked fine on the bench.

So anyway, it looks like the problem is in the module after all.

Next up I will replace the relays in the module and report back.

 

I went ahead and did my own relay replacement. I thought I was getting close to being too late to have one of the repair services do the job and get it back in time to be done when my buddy flew in to get his car.

One thing that I think made the job a whole lot easier is this . It's different from other solder removal tools in that it has it's own heating element. You plug it in, lock down the vacuum plunger and place the tip on the soldered prong of the relay. Wiggle it a few times to get the solder melted and release the plunger and it sucks up the molten solder. About four times and the entire hole is de-soldered. Very neat tool. At first, I tried to remove the silicone(?) covering from the solder joints but it was difficult. I tried using the de-solder tool right through the coating and it worked perfectly.

One last tip. I couldn't get the relays to come off with moderate prying so I grasped them with vise grips and wiggled them free. Easy peasy.

After the module was done, everything works just like new. Whoo-Hoooo!

 

Thanks for all this info! Where did you get the relays from and can you please tell me the part(s) number(s). Thanks so much.