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Body Control Module location

Tiny
BLESS2SUCCESS
  • MEMBER
  • 2004 CHEVROLET TRAILBLAZER
  • 4.2L
  • V6
  • 4WD
  • AUTOMATIC
  • 133,000 MILES
I had bought this Body Control Module but do not know where the location is to install it.

https://www.amazon.com/ACDelco-15122670-Original-Equipment-Control/dp/B000EQP3LG
Saturday, February 9th, 2019 AT 4:55 PM

24 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

I posted the procedure for you below.

Why do you think it needs to be replaced?

Roy

BODY CONTROL MODULE REPLACEMENT

REMOVAL PROCEDURE

IMPORTANT:
- The ignition switch should be in the OFF position when connecting or disconnecting the connectors to the body control module (BCM).
- Always disconnect the 40-way body wiring extension FIRST, the 32-way tan connector SECOND and the 24-way gray electrical connector LAST.
- Always connect the 24-way gray electrical connector FIRST, the 32-way tan connector SECOND and the 40-way body wiring extension LAST.
- The BCM can set DTCs with the ignition switch in the OFF position. The BCM has battery run down protection for the courtesy lamp circuit. The BCM battery run down protection cannot detect shorts on inputs or other circuits which the BCM does not control. Use the scan tool in order to activate the POWER DOWN NOW mode. Use the POWER DOWN NOW mode in order to check for current draws on circuits that are not controlled by the BCM, or controlled by the battery run down protection system.
- Do not touch the exposed electrical contacts of the body wiring extension. Do not open the BCM housing. The module does not have any serviceable components. The module may be replaced only as an assembly.

1. Disconnect the negative battery cable.

CAUTION: Refer to Battery Disconnect Caution in Service Precautions.

2. If replacing the BCM on a Chevrolet TrailBlazer EXT or GMC Envoy XL, remove the left second row seat.
3. If replacing the BCM on a Chevrolet TrailBlazer, GMC Envoy or Oldsmobile Bravada, position the left hand second seat to a cargo position.

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4. Remove the rear electrical center cover.

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5. Press down and hold the locking tab (1).
6. Disengage the sliding latch retaining the BCM to the rear electrical center. Slide the latch inboard until fully extended, approximately 40 mm (1.6 in).

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7. Disconnect the 40-way body wiring extension (1) from the BCM.

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8. Disconnect the 32-way tan electrical connector (2) from the BCM.
9. Disconnect the 24-way gray electrical connector (1) from the BCM.

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10. With an upward motion, remove the BCM (1) from the rear electrical center.

INSTALLATION PROCEDURE

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1. Index the slots on the BCM (1) to the rear electrical center.
2. Using a downward motion, install the BCM to the rear electrical center.

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3. Connect the 24-way gray electrical connector (1) to the BCM.
4. Connect the 32-way tan electrical connector (2) to the BCM.

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5. Connect the 40-way body wiring extension (1) to the BCM.

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6. Engage the sliding latch fastening the BCM to the rear electrical center. Slide the latch outboard until the locking tab (1) is fully seated.

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7. Install the rear electrical center cover.
8. If replacing the BCM on a Chevrolet TrailBlazer, GMC Envoy or Oldsmobile Bravada, position the left hand second seat to a passenger position.
9. If replacing the BCM on a Chevrolet TrailBlazer EXT or GMC Envoy XL, install the left second row seat.
10. Connect the negative battery cable.
11. If installing a replacement BCM, program the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration. See: Vehicle > Programming and Relearning
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Saturday, February 9th, 2019 AT 5:11 PM
Tiny
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Thanks for the steps I will sure hold on to them. But as for replacing the BCM my dash lights, power windows, locks, A/C, radio and mirrors are not working and I figure it might be the BCM.
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Saturday, February 9th, 2019 AT 5:29 PM
Tiny
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They are all controlled by those modules.

Roy
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Saturday, February 9th, 2019 AT 5:39 PM
Tiny
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Hey Roy, do you know how to program the BCM for the vehicle listed above?
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Saturday, February 9th, 2019 AT 5:44 PM
Tiny
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Yes, but you need to have an advanced scan tool, access to GM web site to download the program to install.

It would be cheaper to have someone do this part of the repair.

Roy
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Saturday, February 9th, 2019 AT 5:54 PM
Tiny
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Okay, for example if its not the BCM that is causing these interior accessories not to work could it be the fuses in the rear fuse box that need to be replace?
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Saturday, February 9th, 2019 AT 6:01 PM
Tiny
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I doubt it as that would mean there are a lot of bad fuses failing at the same time.

Did you have the body control module checked for codes?

A code reader will not read the system. You need an advanced scan tool to access the system.

Roy
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Saturday, February 9th, 2019 AT 6:12 PM
Tiny
BLESS2SUCCESS
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I'm going to have to buy me one of those a advance scan tool. Where can I buy one at and what is the best one to use because just the sound of it having one will easily solve problems easily.
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Saturday, February 9th, 2019 AT 6:16 PM
Tiny
ASEMASTER6371
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Look one line. Snap on, Tech 2 are the best. They go for about $2,000.00 to $3,000.00 for a good one but the tools can be had for far less money on Amazon or eBay.

Roy
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Saturday, February 9th, 2019 AT 6:20 PM
Tiny
BLESS2SUCCESS
  • MEMBER
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I bought a used BCM off eBay for the meantime to get my electrical accessories back again. But still waiting for the brand new one to arrive sometime next week. Will the used BCM need to be re-programmed. Do I need to disconnected to battery before installing?
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Friday, February 15th, 2019 AT 7:22 PM
Tiny
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Yes to both. It needs to be programmed to your VIN number.

Roy
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Saturday, February 16th, 2019 AT 3:07 AM
Tiny
BLESS2SUCCESS
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Hey ! Roy both my brake lights and turning signal lights work but not my tail lights. Could this be cause by the BCM also?
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Saturday, February 16th, 2019 AT 3:16 PM
Tiny
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No, the BCM has no control over the lights.

I attached a wire diagram for you to view.

Roy
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Saturday, February 16th, 2019 AT 3:22 PM
Tiny
BLESS2SUCCESS
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Hey ! Roy, I fixed the issue. All this time it wasn't the BCM causing my electrical accessories not to work, it was the 125 amp fuse the had gone bad. My mechanic did a diagnostic test and tested it with a fuse tester and replaced it. Now all the electric accessories back working again.
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Monday, February 18th, 2019 AT 2:06 PM
Tiny
ASEMASTER6371
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Good.

What concerns me is that fuse being bad would have shut off all power to the car and you would have nothing.

There has to be more to the story than the fuse.

Roy
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Monday, February 18th, 2019 AT 2:14 PM
Tiny
COOLCELL
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OK, This is a weird one! Brace your self!
My 2005 Chevy Trail Blazer ext sl.
To started the vehicle have to click the drivers door unlock button or the key fob unlock button then turn the key or nothing happens?
Sometimes if the key is in acc. Click the driver unlock button the starter will try to start.
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Monday, November 11th, 2019 AT 11:30 PM
Tiny
COOLCELL
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I have access to a friends Tech2. Have not asked him but can a Tech2 reprogram a used PCM or ECM on my vehicle?
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Monday, November 11th, 2019 AT 11:35 PM
Tiny
ASEMASTER6371
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Yes it can. You need to program the body control module.

Roy
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Tuesday, November 12th, 2019 AT 1:07 AM
Tiny
COOLCELL
  • MEMBER
  • 16 POSTS
Roy,
Do you think my 2005 trailblazer issues maybe the pcm? Having to press the key fob unlock button to start the vehicle or the ecm?
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Tuesday, November 12th, 2019 AT 1:38 AM
Tiny
ASEMASTER6371
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You are welcome to start a new question at the beginning and we can continue.

This question is for the original person posting. Please start a new question and we would be happy to assist.

Roy
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Tuesday, November 12th, 2019 AT 4:12 AM

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