RAP not working? Fuse good.

Wilmero · November 12, 2005

A friend of mine has a 2000 S-10 and has lost his r.a.p. and his dome lights don't automatically turn on when he opens his door but he can turn them on with the inside button next to the dimmer switch on the left side and when he gets back out and into his truck again, they don't turn on like they should. Is this related to the retained accessory power issue in any way? All fuses test good. Can anyone suggest a good starting point to troubleshoot this? I did try the search feature of this forum with no success, so if I overlooked the topic maybe someone can point me in the right direction. Thanks

GM-Tech · November 12, 2005

These can be confusing if you have no way to monitor the BCM to see what the inputs are doing.

The BCM operates both the courtesy lamp relay and the RAP relay, based on various inputs and timeouts. There are door jamb switches and there is a switch in the door handle. RAP probably doesn't work because the BCM is getting an input that's telling it a door switch has been activated. There's also a inadvertant power relay that will disable the dome lights if they've been left on and 20 minutes elapse.

If you don't have access to a scanner where you can look at the various switch inputs, you can then only go to the various pins on the BCM to test the inputs to see if you're getting what you should.

Wilmero · November 13, 2005

These can be confusing if you have no way to monitor the BCM to see what the inputs are doing.

The BCM operates both the courtesy lamp relay and the RAP relay, based on various inputs and timeouts. There are door jamb switches and there is a switch in the door handle. RAP probably doesn't work because the BCM is getting an input that's telling it a door switch has been activated. There's also a inadvertant power relay that will disable the dome lights if they've been left on and 20 minutes elapse.

If you don't have access to a scanner where you can look at the various switch inputs, you can then only go to the various pins on the BCM to test the inputs to see if you're getting what you should.

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Thank You for your reply, we don't have access to a scanner to test the BCM. My next question is: Would it be wise to take to a dealer to fix the problem? Or is there something we can try ourselves? My buddy has aftermarket insurance with a $100 deductible...would it be worth the hundred bucks to have it taken care of as opposed to trying something ourselves?

GM-Tech · November 13, 2005

Would it be wise to take to a dealer to fix the problem? Or is there something we can try ourselves?

I dunno. How sharp are you guys when it comes to electrical diagnosis?

If you want to try something, go to the BCM on the right side of the dash, pull connector 3 off (purple) and test terminals B2 and B4 and see if either is grounded. Oh, and make sure you make this test with all the doors closed or one or both WILL be grounded. With all doors closed and no outside handles lifted, neither should be grounded.

Wilmero · February 6, 2006

Would it be wise to take to a dealer to fix the problem? Or is there something we can try ourselves?

I dunno. How sharp are you guys when it comes to electrical diagnosis?

If you want to try something, go to the BCM on the right side of the dash, pull connector 3 off (purple) and test terminals B2 and B4 and see if either is grounded. Oh, and make sure you make this test with all the doors closed or one or both WILL be grounded. With all doors closed and no outside handles lifted, neither should be grounded.

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Well, my buddy took it to the dealer so they could test it and they said that there was a short somewhere and that the BCM wasn't getting any power. Is it common for them to just go out? Is it something we can change ourselves? The dealer also told him that when he buys another one $500, that it also needs programing. Do they all need programming? Can we take one off of another 2000 S-10 with the same options and just plug it in?

Thanks for any reply.

JimG · February 8, 2006

they said that there was a short somewhere and that the BCM wasn't getting any power

If the BCM is not receiving power, how will a new BCM fix this? If the short is external to the BCM - i.e., somewhere in a wiring harness; then a new BCM will do nothing for you until the short itself is repaired.

In the event the BCM has an internal short, then you do need a new BCM. Programming is definitely required for any new BCM - it's a computer and they don't do much until you put some code on them. As for the used BCM approach - it may work but I'm not a fan of the idea. This approach has a better chance of working on pre-2002 vehicles. After that year, GM passes the VIN b/t the PCM (powertrain control module) and BCM. If you replace one, the vehicle doesn't start until you perform a relearn.

You might be able to get a new BCM from www.gmpartsdirect.com (look for link on left side of this webpage) if you can get them the part number or email them with all the vehicle info, including the VIN.