2003 3.4 BCM Replacement - Page 2 - Chevy Impala Forums
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post #16 of (permalink) Old 06-08-2012
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Quote:
Originally Posted by kingnutin View Post
I would just replace it in their parking lot, it only takes like 5 minutes and no tools.
Really? That's it? Hmmmm... I'll have to test myself.

I do do all of my own maintenance (struts, brakes, you know), but I've never even seen the BCM. All I know is that it's under the air cleaner... Is there a step by step anywhere on the forums for this? Haynes is kinda vague.

Lol, I said "do do."

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post #17 of (permalink) Old 06-11-2012
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No, the PCM is under the aircleaner, the BCM is under the dash on the drivers side. Look at the first post in this thread, don't worry about disconnecting the battery cable.

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post #18 of (permalink) Old 07-23-2016
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I know this is an old thread, but I managed to fix mine by removing the bcm from its holder and resoldering all the joints for the connectors. There were at least 2 cold solder joints. The problem would only happen on sunny days when the car would get hot inside. Try unplugging the unit and plugging it back in 1st. That would let ours start up and run normally. Of course try at your own risk, but if the controller is bad and you can solder printed circuit boards properly, you really have nothing to lose.
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post #19 of (permalink) Old 02-06-2018
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Bumping this old thread for a couple things. 1. They're selling preprogrammed BCMs online so installing the BCM before programming might be necessary. You give them your VIN and they program it for you ahead of time. 2. Looks like they're selling cheap Tech 2s now for under $400.
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post #20 of (permalink) Old 08-25-2019
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Figured it was worth a shot as suggested by shamoo. I cleaned and re-soldered all the connector pins on the BCM PCB. No change to faults I'm having with my 2002..

DIC dead.
Cruse control stopped working.
HVAC has a mind of its own - recirc, A/C buttons do nothing but it'll randomly switch from recirc to fresh and run the AC so I pulled the fuse that allows the A/C pump to run because it would engage the pump when the HVAC fan was off.

^ These three things all stopped working properly at the same time one day about two years ago.

More recently, occasionally displays low fuel, low brake fluid or door ajar when none of those conditions are true.

Displays service vehicle soon in-between cycling between security and the battery symbol, this was the most recent thing to start happening a - I bypassed the problematic passlock about 6 years ago with a fixed value resistor and never had a problem with it or a warning message displayed until about 4 months ago.

I've pulled every fuse and checked it, none are bad.

Swapping the Overkill PCM out for the original PCM that I kept, no difference except I forgot how rough the factory tune idle is, yuk!

Scanned for codes at different times, none stored.

At the very least the car starts and runs fine still.

I got a recall notice about the dodgy spark plug retainers, I'm thinking I'll get it in to the local Chevy dealer for that and ask them to diagnose the BCM and replace it if its bad.

I keep seeing people mention you can get pre-programmed BCMs with your VIN, but I cant find anyone that offers this.
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post #21 of (permalink) Old 08-25-2019
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Quote:
Originally Posted by Lonney View Post

1. DIC dead.

2. Cruse control stopped working.

3. HVAC has a mind of its own - recirc, A/C buttons do nothing but it'll randomly switch from recirc to fresh and run the AC so I pulled the fuse that allows the A/C pump to run because it would engage the pump when the HVAC fan was off.
I'm thinking bad ground somewhere under the dash. Do you have any schematics for the car? They might be helpful, but even without them, you can inspect the wiring harnesses under the dash.

Start at one of the failing units, such as the HVAC controls, and trace the harness back from it looking for a connection to ground. I'm guessing a ground wire broke loose from its eye terminal, and that is causing the DIC and cruise failures, and wonky HVAC.

HTH.

Doug

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post #22 of (permalink) Old 08-25-2019
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Originally Posted by plano-doug View Post
I'm thinking bad ground somewhere under the dash. Do you have any schematics for the car? They might be helpful, but even without them, you can inspect the wiring harnesses under the dash.

Start at one of the failing units, such as the HVAC controls, and trace the harness back from it looking for a connection to ground. I'm guessing a ground wire broke loose from its eye terminal, and that is causing the DIC and cruise failures, and wonky HVAC.

HTH.

Doug

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Thanks Doug,

I don't have a schematic, I took a quick look around up under the dash, but cant spot any grounding points, this looks like a very time consuming exercise with out information on where all the grounding points are.
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post #23 of (permalink) Old 08-27-2019
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Quote:
Originally Posted by Lonney View Post
Thanks Doug,

I don't have a schematic, I took a quick look around up under the dash, but cant spot any grounding points, this looks like a very time consuming exercise with out information on where all the grounding points are.
I found some ground drawings for the 3 items: DIC, HVAC and Cruise (CCM). Post or PM me your email and I'll gladly send them to you.

Checking them, it's not obvious where the problem might be. Ground G201 is shared between the BCM and the HVAC. G203 is shared between the BCM and DIC. Both of these are located above the driver's knees as best I can tell from the attached pic.

I would check there first.

Doug

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post #24 of (permalink) Old 08-27-2019
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Quote:
Originally Posted by plano-doug View Post
I found some ground drawings for the 3 items: DIC, HVAC and Cruise (CCM). Post or PM me your email and I'll gladly send them to you.

Checking them, it's not obvious where the problem might be. Ground G201 is shared between the BCM and the HVAC. G203 is shared between the BCM and DIC. Both of these are located above the driver's knees as best I can tell from the attached pic.

I would check there first.

Doug

.
Awesome, thank you Doug! PM sent with my email.
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post #25 of (permalink) Old 08-29-2019
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Today I took things apart, cleaned G201 and G203, added star washers and greased everything with Jet-Lube SS-30 pure copper anti-seize (I happen to have).

No change, as soon as the key was turned around to ON the security/battery/service soon messages came back, and the radio would cycle between locked and on every few seconds.

Since things were apart already I figured I'd take the dash apart, get the radio out and give G202 (https://www.impalaforums.com/chevy-i...ml#post1564578) a clean, star washer and a dab of copper anti-seize.

Put everything back together, for now at least the security/battery/service soon messages didn't come back and the radio was behaving it self. I was able to get into the settings and reset the oil life warning - something I've not been able to do since the security/battery/service soon messages appeared a few months ago. So some progress, hopefully permanent.

However the DIC is still dead, HVAC still in lala-land. I think when I get the car in for the two recall items (spark plug wire retainers and unintended key rotation), I'll ask them to do a diagnostic on the BCM to see if thats part of the problem or rule it out.
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