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Ask Don 'Mo Lurch' Your Own Que...
Don 'Mo Lurch'
Don 'Mo Lurch', Auto Mech / Electronics
Category: Chevy
Satisfied Customers: 20516
Experience:  Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.
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Chevy Silverado 2500HD LB7: Rear power doors not working

Customer Question

Rear power doors not working
Submitted: 7 months ago.
Category: Chevy
Expert:  Don 'Mo Lurch' replied 7 months ago.
.sorry for the delay.............Greetings...... “Hi, I’m Don (akaCustomer and I look forward to helping you!”.There are "3" Relays that operate the Door Locks, which are activated from the BCM (body control module)1 Relay for Lock (all doors)1 Relay for Driver Unlock (only)1 Relay for ALL UnlockYou need to see & even switch Relays around to be sure the ALL Unlock Relay is clicking & sending Voltage + to the Rear Door ActuatorsThe Door Actuator wiring work like thisPress LockOne wire will have Voltage +One wire will have Ground -Press UnlockThe wire that had Voltage + now shows Ground -The wire that had Ground - now shows Voltage +So, first check & swap Relays aroundIF no difference, remove a Rear Door Panel & test the "2" wires at the ActuatorIF No Ground -, or Voltage + then the BCM needs to be Tested via GM Dealer Scan Tool.IF you need more information, please ask "prior" to Rating..Please do the right thing and leave a rating, using the rating system, so I may be credited for this Q&A..NOTE: Do NOT Rate on how much TIME you waited, because I am not on 24 / 7 and I answer as soon as I see the question.The question will still remain open for follow up questions if needed..If for any reason, you can't rate my answer OKAY, GOOD, or EXCELLENT today.Please reply and let me know why, so I can help more/better..Rating is very Important to our Service.......
Customer: replied 7 months ago.
Are you sure there are 3 relays? I know it has 3 labeled on the drivers side fuse box, but there are only 2 relays (Lock and Unlock) and 2 fuses (10A PDM and 20A Locks) that I have found related to the locks. There is no Driver Unlock relay.The front doors both work without the relays or the 20A lock fuse. The only one that effects the front locks is the 10A PDM.
Customer: replied 7 months ago.
Attached is the fuse box. 2 relays and 2 fuses circled.
Customer: replied 7 months ago.
It sounds like I need someone else who knows the silverado a little more. Based on your response, everything you covered I already had said I confirmed other then taking it to have it scanned with a GM Dealer Scanner.
Customer: replied 7 months ago.
Don't bother spending any more time on this one.
Expert:  Don 'Mo Lurch' replied 7 months ago.
wow...........thanks for asking for more info......Please show me where you "actually tested" the Actuator wires.Sorry you did not understand the way the System worksMy answer was correct & to the pointthanks
Customer: replied 7 months ago.
I tested the actuator wires at the actuator. I DID understand the way the system works. Everything you mentioned is what I had already said I did prior to your initial response minus taking it to a GM scanner. I was just hoping for a lot more specific knowledge on the Silverado and the Silverado's locking system (there is only the 2 relays). No hard feelings. Thanks for trying.
Expert:  Don 'Mo Lurch' replied 7 months ago.
sorry............with your clarification, apparently you have the "YE9" Option & NOT Standard "3 Relay"I would not know that without the clarificationEither way the Door Locks have to have Input from the BCM thru DATA in which the Door Lock Button supplies a pulse Ground to the BCM, then from the BCM the signal is sent to either Ground for Lock or Unlock at the Actuators.As stated the Rear Door wires at one of the Actuators need to be tested for "Reversal Rest at Ground" Circuit as I described in my first answerThis way you can see if it is a Harness Connection issue or the BCMHere are Schematics, in case you do not haveClick Attachments belowsorry for the issue, but we cannot see or touch the vehicle & depend on customer to supply as much info as possiblethanks