Keyless entry fob & BCM?

tjkeno
Posts: 6
Joined: Sun Nov 17, 2013 8:57 am

Keyless entry fob & BCM?

Unread post by tjkeno » Sun Nov 17, 2013 9:43 am

Hello all -- very happy to have found you.

My car is a 2003 Pontiac Grand Prix GT 4-door sedan. Purchased used, with SRS trouble light lit up on dash. After the first rainstorm, the front carpeting was very badly soaked. Tried cleaning sunroof drains, but finally ended up sealing it closed with marine repair silicone.

Now to my present problem. GM dealer confirmed from the VIN that the car is wired for a factory remote. Seller did not have a keyless entry fob, so I bought one online. Followed programming instructions to the letter, but it did not respond with a beep when it was supposed to.

1. Does the fob and its programming interact with/through the BCM?

2. Is what is under the passenger seat the BCM or is it some module that "reports" to the BCM?

3. Is the SRS dash trouble light controlled/activated by the BCM?

4. If I repair/clean/replace the under-seat module, will that alone clear the trouble light?

5. Can I send the BCM off for a $50 reset and solve this issue?

6. Would the existing SRS fault cause the BCM to reject the remote programming?

Although I'd really like to have a remote, I don't see the percentage in spending more than $50 to get a $20 fob to work.

Thanks.

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TerryAuto
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Joined: Fri Dec 11, 2009 8:48 pm

Re: Keyless entry fob & BCM?

Unread post by TerryAuto » Sun Nov 17, 2013 4:15 pm

Can you confirm the learn procedure went into learn mode? This usually is the doors will lock then unlock signifying it is in learn mode.
The module under the seat is the airbag module, yes. The water has contaminated it. It must be replaced. This has nothing to do with the remotes.

tjkeno
Posts: 6
Joined: Sun Nov 17, 2013 8:57 am

Re: Keyless entry fob & BCM?

Unread post by tjkeno » Sun Nov 17, 2013 6:53 pm

TerryAuto wrote: Can you confirm the procedure went into learn mode? This usually is the doors will lock then unlock signifying it is in learn mode.

The module under the seat is the airbag module. This has nothing to do with the remotes.
Thanks for your response.

In the procedure I followed, there is no mention of the doors locking then unlocking. Assume you meant by themselves, under BCM control.

I'm not sure a blanket statement like "... has nothing to do with the remotes." is totally correct. While the airbag system and the door lock/unlock system may not communicate directly with each other, they might very well both communicate with/through the BCM.

If the BCM has logged a trouble code from the airbag, could that be what is preventing it from entering programming (learn) mode?

My instructions, printed out at a GM dealer, say in part:

5. Turn ignition to ACC. The body control module (BCM) will perform the following to identify the type of BCM installed: Flash the seat belt indicator 1, 2, or 3 times. Chime 1, 2, or 3 times.

6. Turn ignition to OFF, then back to ACC within 1 second. The BCM may begin to chime and flash diagnostic trouble codes (DTCs). If the BCM has stored any DTCs, refer to Diagnostic System Test - Body Control System.

7. Open and then close any door. The BCM will chime to confirm that programming mode has been entered.

When I do #5 above, the flash and the chime each occur 3 times.

When I do #6 above, nothing happens -- no flashes, no chimes. But the instructions do say MAY.

When I do #7 above, nothing happens -- no chime.

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TerryAuto
Posts: 313
Joined: Fri Dec 11, 2009 8:48 pm

Re: Keyless entry fob & BCM?

Unread post by TerryAuto » Sun Nov 17, 2013 8:03 pm

Don't like that blanket statement, well its true. The Airbag module has nothing to do with preventing a remote from being programmed. Yes, all modules communicate with each other- how insightful.

Make sure when you open the door in step 7, the dome lights come on.
If the BCM will not enter remote programming mode- which it isn't, it may be faulty. Maybe that's why the car did not come with a remote- they didn't work so the last owner threw it out or took it off his key ring.

You are going to have to look at BCM data stream to go any further diagnosing the programming problem.

tjkeno
Posts: 6
Joined: Sun Nov 17, 2013 8:57 am

Re: Keyless entry fob & BCM?

Unread post by tjkeno » Sun Nov 17, 2013 9:27 pm

TerryAuto wrote: The Airbag module has nothing to do with preventing a remote from being programmed.

Make sure when you open the door in step 7, the dome lights come on.

If the BCM will not enter remote programming mode- which it isn't, it may be faulty. Maybe that's why the car did not come with a remote- they didn't work so the last owner threw it out or took it off his key ring.

You are going to have to look at BCM data stream to go any further diagnosing the programming problem.
I'm not saying that the airbag module itself is preventing a remote from being programmed. I'm trying to find out if the presence or existence of a fault caused by the air bag module is captured or logged or whatever by the BCM, and then if that is what is preventing the BCM from entering the programming mode.

The dome lights do come on in step 7.

If the BCM itself is faulty, it seems like there would be other symptoms indicating that. Everything else on the car works -- no DTCs, no SES light, nothing like that. The previous owner did not give me a remote. I'm sure he knew about the leaking sunroof, and did not want to let on that the remote no longer worked. GM dealer verified that the car is wired for keyless remote -- lock/unlock/trunk/horn.

What is required to look at the BCM data stream? Dealer only scanner etc?

tjkeno
Posts: 6
Joined: Sun Nov 17, 2013 8:57 am

Re: Keyless entry fob & BCM?

Unread post by tjkeno » Tue Nov 19, 2013 12:08 am

UPDATE

Went to the same GM dealer where I got the fob programming instructions. He printed out this regarding the airbag Sensing and Diagnostic Module (SDM) under the seat:

Important
The AIR BAG indicator may remain ON after the SDM has been replaced. If so, perform the following procedure in order to update the BCM with the new SDM part number. After programming the SDM part number into the BCM, cycle the ignition switch OFF and ON. This turns OFF the AIR BAG indicator and clears the DTC. Other subsystems that interact with the BCM must have ALL DTCs CLEARED (caps added) before programming the BCM.

Procedure
Install a scan tool.
Select the Special Functions option from the SIR Menu and press enter.
Select the Setup SDM Part Number in BCM option and press enter.
Follow the procedure on the scan tool display.
Cycle the ignition switch OFF and ON.

I just had a gut feeling that there was some kind of "conversation" going on between the SDR and the BCM. Unfortunately of course the scanner is a Tech-2, not something every parking-lot mechanic has. Maybe I can sell the new fob on Craigslist. :-(
.

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carriedi
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Re: Keyless entry fob & BCM?

Unread post by carriedi » Tue Nov 19, 2013 11:29 am

BCM is connected to the airbag module with a black and white wire that gives the air bag module information on the seat belt status.

if the air bag light is on, did you have it scanned to see if a code is set?

there are independent shops that have tech2 scanners you might call around and ask if they have one to scan your vehicle. While Snap On, OTC and Bosch (vectronix and now owns SPX too) make great scanners sometimes you just need a tech2
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