Right rear door ajar message

[John-1500HD]

I’m troubleshooting a Right rear door ajar message  on my 2003 Sierra 1500hd.  I’ve looked at the wiring diagram and am more confused now! Here is what I have done and the results:

All doors closed, start truck, put in gear, receive message: Right rear door ajar. 

All doors open, start truck, put in gear, receive messages for each door...which is what I would expect 

I then unplugged the connector to the BCM (located above the brake pedal) and did the following test:

All doors closed, start truck, put in gear, receive message: Right rear door ajar.  ??? How does it know anything?

All doors open, start truck, put in gear, receive messages:  Driver D A, Pass D A, Right rear door ajar .  How does it know? Why did it not say the left rear door was ajar?

I opened the door panel and verified the ground was good and then it got more weird.  According to the wiring diagram, the lead going to the BCM from the Right rear door is Lt. grn/blk. Well it is Lt.grn/blk at the BCM connector, but at the door it is Lt.blu/blk.  

So I checked the left door. Diagram says it is Lt. Blu/blk and that is correct/ what I found.

Conclusion:   Even though I was surprised by the wire color everything toned out ok.  So while I think the problem is with the door latch or the BCM, I really need some suggestions.

[Supreme Pizza]

I would use a volt meter to confirm that the door switch is functional. 

 

 

 

 

[John-1500HD]

I’ll show my ignorance in the electrical field now.  In testing the switch am I looking for voltage or some level of resistance (ohms)?  And I’m guessing the best way to do this is go to the BCM connector?  Thank you for your suggestion.

[Ak_grown]

you tested the ground side of door latch? did you test the bcm side of door latch?(at the latch) leave door open and use screw driver to latch the door latch closed and get reading. verify voltage change, no change, replace latch. if latch works as designed check other modules that connected. 

[Supreme Pizza]

 

 

 

https://www.amazon.com/Voltmeter-Ammeter-Electrical-Digital-Multimeter/dp/B00N3KQ4IG/ref=sr_1_3?ie=UTF8&qid=1526851214&sr=8-3&keywords=volt+meter

 

 

 

 

 

[Supreme Pizza]

I can not say for sure how your specific door switch works. It may ground to show the ECU that it is closed. Or it may break the ground connection. Might send a 12V positive to the door and the voltage is either supplied or cut depending on the door position. Once you figure out which, you can determine the voltage or continuity of the situation.