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I have a 2008 Chevrolet Impala LS with approximately 80,000 miles.

I've noticed that both front door power locks are not working properly when it's very warm out, especially if we're parked in the sun.

My wife first noticed it because the remote fob wasn't working for the driver's door. I did further testing and confirmed that using the switches on the inside of either door also present the problem.

Once every 3-5 minutes, I can use the switches to either lock or unlock the front doors. After that, they stop working until I wait again, as if they've lost their charge. At first, when they're not working, I can see the locks shake as the motor moves but they don't go up or down. Continued attempts are silent: you can't hear or see the motor trying to work. After the few minute wait, the front locks work fine, once, as if there is no problem at all.

My suspicions about this being heat-induced have been confirmed, because this problem now occurs every day the outside temperature is above about 80° F, and less if in direct sunlight. There has also been at least one time when it spread to affect one of the rear locks when it was especially hot. Knowing heat exacerbates the issue doesn't, however, help me source the issue.

I don't think this is a motor issue, as the motor works fine when it seems to have power. Outside of that, I don't know how to troubleshoot where the problem is occurring. I have read that there are wiring issues common with GMs around this year model.

How do I troubleshoot and/or diagnose this issue?

More details on what is working:

  • All other power features work fine.
  • Door, lock and power fuses are fine.
  • Rear doors are 100% unaffected and fine.
  • Manually moving the locks works to correctly lock/unlock the door.
  • Using the key in the driver's side door works to unlock the driver's door.
  • Ignition on/off doesn't affect the issue.
  • I swapped out the power lock relay in the console fuse box with another working one, with no effect. Relay seems to be working fine.

When you hit the indoor switches once, with a door open, they do not lock immediately. This is a feature of the car, and normally works fine. However, with my problem, if there isn't a "charge" the locks won't lock after the normal 30 seconds or so, but they will lock after the 3-5 minutes, as if the lock order had been queued until power was back to the switches. When it finally activates, all locks successfully lock.

Additionally, if the key is not in the ignition and one door is open, when you press the lock button sometimes the console will chime, and nothing else happens. This is not the typically warning chime from locking your doors, but more like the console alert chimes such as "wiper fluid low".

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    This sounds like an issue with the Body Control Module (BCM). It could be due to a faulty ground or some other reason. One thing you can try is to disconnect the batter and let the vehicle sit for ~30 minutes. This might reset everything and get it back to functioning. If not, it's going to be very hard to diagnose. – Pᴀᴜʟsᴛᴇʀ2 Jul 13 '15 at 17:14
  • @Paulster2 Thanks for the tip. I'll try disconnecting the battery tonight when I get back home. If it is the BCM, is there anything else I can try, in addition to the disconnect, to test to confirm it's the problem? However, if there's an issue with wiring, contacts or other electrical, this won't help, will it? – Web Head Jul 13 '15 at 17:54
  • Disconnecting the battery will not help with wiring, contacts or other electrical issues. I'm doubting it will help in your situation, either, but it's worth a try. – Pᴀᴜʟsᴛᴇʀ2 Jul 13 '15 at 18:18
  • @Paulster2 I didn't get to the battery, b/c of the other things I tried last night and then needing the car. But, as of today (which has been cooler), the problem seems to have gone away, so I can't really troubleshoot any further. – Web Head Jul 14 '15 at 20:13
  • You just have to love intermittent issues. Hardest thing in the world to diagnose. – Pᴀᴜʟsᴛᴇʀ2 Jul 14 '15 at 20:15
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I just replaced all 4 door lock actuators on my f350 for being weak. They sounded like they were trying and they did make the locks move but not go up or down fully. I'd say the 2 your having problems with are weak and the heat just makes it worse. Pull your door panel off and follow the mechanism for the locks till you find the actuator. Mine were $35 for all 4 and it'll take a couple hours generally.

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If it gets better with the engine running suspect the battery of not having high enough voltage but still putting out the current for the starter (possible bad cell).

Heat could be breaking a specific circuit that is responsible for mainly powering the actuators, check the voltage and amperage at the actuator when it is working properly and when it is not. Capacitors store the energy but quickly discharge if there is not much current to recharge them which gives you that winding down feeling.

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