How to diagnose power door lock issues on 2008 Chevy Suburban
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Keyless entry began to not lock/unlock the rear doors and then eventually stopped working all together with all doors. When the lock button is hit manually, there is a clicking sound coming from where the driver door wiring harness enters the fuse box. Put new battery in remote and pulled every single fuse inside and under hood, all good. Even though it doesn't physically lock the doors, the alarm will still sound when entering vehicle. Is there a relay etc to check or unfortunately the door actuators?
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Checking for power and ground at the actuator is something that you can do depending on switch position - if you are getting the power to work the actuator and it doesn't work -- then the actuator itself has failed. Since you are saying all the doors are not working, and there is some kind of alarm -- is it a factory alarm? Aftermarket installed alarm? -- I would lean towards your concern being related to the installed alarm (if that's the case) or it could be that all the actuators have failed. Alternatively, you could have a master switch issue.
Either way, you have to get the door panels off -- at least the driver's one to start with -- and do some circuit testing.
It is just the factory alarm horn blowing when door is opened while "supposed" to be locked but isn't really because lock button just makes the clicking sound. Vehicle thinks it is locked but really isn't so horn will sound if doors opened in lock mode is all that is.
Turn key on - do not start engine ... While observing the dome light - manipulate door lock buttons to see if light dims ever so slightly with each lock / unlock button cycle.
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That indicates the door lock actuators are not attempting to operate at all - otherwise the light would have dimmed *ever so slightly* - make sure your test is confirmed and you are satisfied the light doesn’t dim - *slightly* - it will not be abundantly conspicuous - dome light will dim very little and is easily overlooked.
You should use the link below and re-check all related fuses - there are more than you think - *TEST* fuses using a 12 volt test light - do not rely on visual inspection!
https://www.autogenius.info/chevrolet-suburban-2008-fuse-box-diagram/
Finally - a professional quality scan tool is capable of displaying live BCM data so the operator can determine if the signal is indeed being sent to the lock actuators. - or not - which will narrow the search down considerably.
(BCM = Body Control Module)
It is just the factory alarm horn blowing when door is opened while "supposed" to be locked but isn't really because lock button just makes the clicking sound. Vehicle thinks it is locked but really isn't so horn will sound if doors opened in lock mode is all that is.