Hey guys,

Can anyone help diagnose this recent problem I'm having. The power door lock switches, on both driver and passenger doors, only functions to lock the door but will not unlock. When either switch is depressed to lock, both function with no problem. But when depressing either side button to unlock, there is absolutely no activity at all. Like there is no current reaching either one. This happened once about a week ago, but my son came along and just kept pressing the passenger side button and it came back to life after 5 or 6 tries. But now the same problem has recurred and it will not resolve. Any thoughts would be really helpful. Thanks.

 

I've had the same or at least similar problem with the same voltage truck for about 7 years now. My guess is the locking mechanism is going bad and needs to be replaced.

 

Is there one in each door? If yes, how do I check which one is faulty? By the locking mechanism, are you referring to the actuators (power door lock motors)? If yes, how do I test each of the two to see if they are still good? Although, I was thinking, if the problem is with both switches, and that there appears to be no current reaching either switch when attempting to activate either switch to unlock both doors, could the problem be something else in the circuit and not the actuators at all? For ex., could it be the door lock relays that , I believe, are under the dash on the passenger side? Or the RAP? Or the CSM? Thanks.

 

Do you have remote keyless entry and can you lock/unlock with the fob? Keypad, if equipped?

 

No. Just a key.

 

Check the switch on the passenger side.

 

It is necessary to determine what the configuration was when it left the factory, not necessarily how it was when you got it. There's a lot of differences between the circuitry for a truck with basic power door locks and one with remote keyless. If that distinction isn't known, a lot of time and effort may be wasted troubleshooting the wrong configuration.

 

The factory configuration for my vehicle was basic locks with key. No remote keyless. Confirmed by the dealer with my VIN.

 

I'm thinking if it's the switch on the passenger side, that the switch on the drivers side would work fine, but both switches won't unlock the doors. Not just the one on the passenger side. So, shouldn't it be something else?

Also, the locking mechanisms in both doors are performing the same (lock but won't unlock) so I'm not sure if the locking mechanism needs to be replaced as I would think one would work and the other wouldn't, right?

Saw a youtube video that mentioned relays under the dash as a possible culprit. They're located under the section of the dash (on top) that is scooped out in shape. Anyone know how to check these relays and which might be for the door switches? Any other ideas? Thanks.

 

If you have the non-RAP system, the door switches control the actuators directly, no relays involved.

 

As such, then, does that put the problem back as possibly being one of the 2 switches? Or something else. Thanks.

 

It could be either switch (specific internal failure) or it could be the wiring between the two switches. Since you mentioned a specific prior experience with the passenger side switch and a temporary restoration of operation, I'd start there.

Do you have the service manual or, at least, a multimeter?

 

Multimeter yes. Service manual no, unfortunately.

 

See if this works, there's either an error or an ambiguity in the diagrams for the 99.


Individual switch test, see (crude) image below. Both door lock switches are the same internally.

Ohmmeter checks:

Switch at Rest:
Continuity between pins 2 and 3
Continuity between pins 6 and 7
Pins 2 and 7 open to all other pins

Switch in UNLOCK:
Continuity between pins 4 and 3
Continuity between pins 6 & 7 (unchanged)

Switch in LOCK:
Continuity between pins 4 and 6
Continuity between pins 2 and 3 (unchanged)

 

I would not want to be in that truck as it would be eating switches left and right. If it locks, but doesn't unlock, it is the two UNLOCK Relays that are glitching it up. Swap in two known good relays and test it again