how do I diagnose a body control module?

[rockyfatcat]

I have an 2002 Jeep liberty and the interior lights won't go off. The manual says that with the doors closed and the ignition on the light should go out.

The maintenance manual says either a bad ground. (I don't know where) or to read the BCM input and output codes.

Anybody?

 

[rhbridges]

I'm assuming you made sure the interior light switch is off? You know, the one that usually says On/Door/Off.

The first thing I would do is check the door switches. If one is bad it could think the door is still open.

 

[rbalan]

I'm assuming you made sure the interior light switch is off? You know, the one that usually says On/Door/Off.

The first thing I would do is check the door switches. If one is bad it could think the door is still open.

I agree with checking the door switches. I don't know about Jeep but the BCM may need to be checked by a dealer.

 

[galvatron]

Is the dome light switch on?
Sounds silly but worth checking..... All 3 interior lights are push activated switches, the rear one is easy to hit and then forget about...ask me how I know...... I've got an 04 Libby

Standard bulbs or have they been swapped to LED? The BCM does not play well with LED bulbs..

 

[jeep78]

Do you have a service manual for that Jeep? NVRM, I see you have a manual.

 

[rockyfatcat]

The rheostat doesn’t turn out the light. The door and gate/glass have messages which display where the odometer reads and are not an issue. The last time this happened I replaced the multifunction switch. I have a new one that does not fix it.
The maintenance manual identified these issues and then gives reference to check a body ground and I don’t know where that is.
The only thing left is diagnosing the body control module.

I appreciate the captain obvious input, but was hoping for some ODT brother to help me figure out either what the BCM code was or where I could take it to get the information

 

[rockyfatcat]

Do you have a service manual for that Jeep? NVRM, I see you have a manual.

I was able to read a pdf file online of a manual. i think it was a Colorado4wheel. Com website

 

[Lockout]

Signal coming out bcm for powering dome lights needs to be checked with multimeter

Also you can check light housings
And switch

Also check for water leaking into bcm connector

 

[jeep78]

I think this is one of the grounds:

6. Turn ignition off. Ensure PCM harness connectors are still disconnected. Using DVOM, measure
resistance between ground and terminal No. 31 (Black/Tan wire) on PCM connector C1. If resistance is
less than 10 ohms, replace and program PCM. See appropriate REMOVAL, OVERHAUL &
INSTALLATION article. If resistance is 10 ohms or greater, repair open in Black/Tan wire between
PCM and ground connection. Ground connection is located at ground connection for negative battery
terminal.

Also, I saw reference to a ground connection between the body and the dash. Never saw a location, though. An extra ground strap may be the way to insure bonding of dash and body.

 

[opps]

Is there a Jeep owners forum you can check?
When our old Saturn started flashing outside and inside lights when I turned the key - ch Co the Saturn forums and found out it wa the ECM. Took to dealer and they had to call district to figure out it was the ECM.