I am almost certain the bcm is bad in my 04 Monte ls. Due to the lot were I got it from being jack ***' the harness caught on fire so I replaced the engine harness,PCM, and fuse box.i had to program the ignition to the pcm and Since I've done that the car has been running decent with just a couple minor issues to be worked out.

Is there any programming that needs to be done at the dealership that is crucial?
Yesterday my car wouldn't start and the only light that would come on is the check engine light, I got the car to start again by disconnecting the battery for 10 minutes but according to the research I have done my bcm is bad.

Can I get a bcm out of a donor car at the junkyard like I did the pcm? Will it need to be taken to a dealership to be flashed/programmed to my car? Or is a bcm no good after it has been programmed to its original car? Also the used bcm I would be getting is coming from the same car I got the pcm out of so in theory would it even have to be re programmed? As far as the bcm knows it will be communicating with the same pcm that it always has.

 

Hey Charlie
When the PCM is swapped you need to do a "30 min. security re-learn procedure" to enable the VAT system. A common code is stored and shared shared between the PCM, BCM and the chip in the ignition lock cylinder and passed through the serial data link. Try that first. A bad BCM will throw a code starting with a "B" and usually has multiple symptoms.

Here's the procedure generously shared by MCF member RickCoMatic:

The Security Relearn Procedure. This procedure allows the PCM to function properly in your vehicle after a Battery disconnect or a Security Breach.
Follow the steps listed below completely.

1. Attempt to start the car by turning the key to the Start/Run Position.
2. Observe that the vehicle fails to start and that the security light is illuminated.
3. Release key to the 'ON/Accessory' Position. (DO NOT turn key to the 'off' position, DO NOT remove the key.)
4. Allow the vehicle to sit with the key in the 'ON/Accessory' Position for no less than 11 minutes (the security light should stop flashing, if not wait up to 3 more minutes).
5. Turn key to off position and allow the vehicle to remain in the 'OFF' position for no less than 30 seconds.
6. Repeat #1 - #5 for 3 cycles.
7. On 4th-5th attempt, car should start.

NOTE : Since this is a fairly long procedure, I would limit all electrical sources, such as disconnecting headlights, to prevent discharge of battery.

NOTE 2 : It is SAFE to wait LONGER than the allotted time, but it is not safe to wait less time. I.e. 12 minutes instead of 11 minutes should be safe; however, waiting 10 minutes instead of 11 minutes is not safe.

Properly executed, this procedure should take approximately 35 minutes to complete.

 

It's always tough getting squared-away following harness damage of any kind.
Fire being the worst case.

That it will run, however briefly, ... means you got to be getting close.

Moving forward you are going to need to Plug-in, Read Codes and Troubleshoot.

Bosch-Actron CP9670: AutoScanner Live Data Code Reader 1996-Up OBD-II and CAN | JEGS

 

Charlie, I read your introduction thread after I responded to this one. In that post you explained you already did the 30 min re-learn, and the light problem would also suggest a bad BCM. The ignition switch housing is also a possibility.
The BCM can't be re-programmed without a Tech 2 scan tool and subscription to the GM website. A new BCM requires programming with a Tech 2, no subscription necessary.

Good luck, keep us posted

 

Okay so installing a new bcm requires a program, now can I get a used bcm and drop it in then get reprogrammed?

Also I have suspected the ignition being a source of some problems but I figured i would replace bcm first then the switch because I believe the bcm is causing the most problems right now. Notice I said ignition switch and not the ignition tumbler....is that correct or will I have to replace them both?
I think after I get the bcm replaced and switch I will have a sound running Monte

 

Update

The Monte won't start and the only light that comes on is the check engine light, It did this 3 days ago and I did research and found it was the bcm and guys were unplugging their battery for 10 minutes ad the car would start again so that is what I did. However it did it again today and after having the battery unplugged for a good hour the car didn't start again.

 

I believe a used BCM of the same year, make and model will work to get you to the dealer to have the new BCM programmed. You will probably have some MIL's if some of features and/or settings are different from your car. The program needs to recognize the "Calibration ID" and VIN. You'll definitely need to do a security re-learn. Sorry, but I've only programmed new BCM's which are "blank slate". The process of programming has a long series of questions about your vehicle that need to answer correctly before formatting or some functions won't work.

The Ignition switch housing is usually the cause of electrical/ starting related gremlins, but the ignition lock cylinder (tumbler) contains the chip that stores the VAT code shared with the BCM and PCM.

I'm surprised your not getting a "Security" MIL. That usually comes with a no-start related to the BCM. I kinda' leaning toward the problem being the ignition switch housing. Personally, I would replace that first. Use ACDelco, they last longer.

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