Vehicle: 2017 Chevy Express 3500 LT 6.0L V8

Issue: Power lock switch will unlock doors without issue, but not lock them

Relevant information / diagnostic attempts:

• Both lock and unlock works fine from the remote control (so lock mechanisms are presumably fine)
  
• Doors automatically lock after I've driven a few miles (further evidence the lock mechanisms are fine)
  
• Same issue on both the driver and passenger side. That is:
  • The unlock feature works fine on both the driver and passenger door powerlock switches
    
  • The lock feature does not work on either the driver or passenger side. So this probably isn't an issue with the switch itself. I replaced the driver side power lock switch just in case, issue not resolved.
    
• When I press the lock button, there is no sound whatsoever (no clicking, etc.)
  
• All of the fuses under the driver's seat appear normal
  

My next thought was that this was some sort of "feature" to keep me from locking myself out of the van, but as far as I can tell there is no such feature activated. It also appears that the van is registering all doors to be closed when that's the case (no "door ajar" indication).

I'm at a total loss here. Any advice would be appreciated!

 

Not sure what changed since 2013 but these vans have mostly just changed in powertrain.

I'd try checking grounds.

https://charm.li/Chevrolet/2013/Expr...%20Schematics/

 

Thanks, I'll start checking

 

Does the lock button work from the back door?

These Vans use a ground switch for the locks. That means the locks get constant power and the ground is what switches them. When you hit the button it grounds one of two wires for lock or unlock. If you ground that wire anywhere it will operate the lock.

The only lockout protection I'm aware of is that it won't let you lock the doors with the key in the ignition if the driver's door is open. In that case they'll lock and immediately unlock. There are settings in the information center for the door locks but I can't remember exactly what they are. I turned off the function that unlocks the doors when you put it in park but I haven't looked at it since.

I know if you pull one of the switches you can ground the wires and operate the locks. My slider door has to be closed to operate the power locks as it makes connection at the door jam rather than through a cable. Not sure how the side barn doors work.

 

Yessir, same symptoms for the switch on the back door. I'll start investigating the ground.

 

Yeah so I had a similar issue with my 2022 Silverado a few weeks ago, turned out it was just a faulty sensor on the door, got it replaced and the Powerlock system's working fine now. Make sure it's not just a simple glitch, but that'll get you pointed in the right direction.

 

Thanks for that. For your Silverado is the sensor part of the latch? Or a separate pressure switch? For this van it's built into the latches for the front, passenger, and cargo doors, but there's the traditional pressure switch for the side doors. The dome light turns on/off at the appropriate times when doors are opened or closed, so I assumed that wouldn't be the problem. Did your truck present the same way?

So far all ground appears fine, but I'm still investigating.

 

Yeah, I've seen that Powerlock issue creep up on a few gen 2 Blazers, but most of the time it's just a faulty solenoid or a loose connection somewhere. Try swapping out the solenoid and see if that clears it up, might save you a diagnostic fee down the road.