I have a few issues and wonder how many tie back to the g.e.m.
*battery light stays on but although charges fine and battery is good
*fuel Guage doesn't work and low fuel light stays on
*Rear wiper don't work
*rear hatch button on dash dont work (button on tailgate does)
*Front wipers sometimes work sometimes don't
*The alarm works But the truck won't go onto program mode for the fob (keyless entry module was changed out and tried in another vehicle and is good)
*Abs and red brake light on dash on and off together sporadically
*Radio and windows turn off with the ignition switch without the normal delay or when open door
*don't have to press brake to shift
Stuff like that...
Could a faulty g.e.m. be the culprit?

 

What is a g.e.m.?


George

 

My wife is a gem. I, too, don't have a clue what a g.e.m. is either, let alone how it relates to Blazers and Blazer type vehicles.

 

You better not tell your wife that you don't know what she does. LOL.


George

 

Generic electronic module or body control module or whatever...

 

Ah, the BCM (body control module). Yes, at least in the GM service manuals many of us have, they are called BCMs. And yes, the BCM is connected or runs many of the items on your list. Instead of the BCM being bad, perhaps there is a fault in the wiring harness or you have some bad/corroded connections?

If you supply the year of the Blazer and other info, many of us can scrounge up the info from our service manuals.

 

BCM, got it. As Christine said get us a year and we can help you work through the list.

George

 

2000 Blazer, ZR2 , 4x4, Automatic
thank you so much

 

This quite a list. I can help you with the whole thing depending on how deep you want to get into it.

The BCM is involved in parts of this list:

1. Rear hatch button
2. Key FOB
3. Delayed power

The VCM (engine computer) is involved in:

1. Battery light
2. Fuel gauge

The class 2 serial data bus is involved in:

1. Battery light
2. Fuel gauge
3. Brake lights

The fuel gauge can also be the fuel pump/sender in the tank

The rear wiper can also be:

1. Dash switch
2. Rear gate cutout switch
3. Motor

The rear hatch can also be the dash button

The front wipers can be the MF switch or motor

The ABS light can also be ABS system problems

The delayed power issue can also be the relays

The brake shifter issue can be:

1. Shifter solenoid
2. Brake switch

Every problem can be:

1. Fuses
2. Power
3. Grounds
4. Wiring

If you swap out the BCM as a trynostics experiment the truck will not run and you will need to reprogram the passlock system

The first thing I would do is:

1. Check every fuse in the UHFB and the accessory panel in the side of the dash
2. Check the grounds on the engine block
3. Hook up a scanner to the DLC port and monitor live data to see if you get any dropouts as a first order check of the class 2 data bus integrity

After that if you give a prioritized list we can work our way through your issues.

George

 

In answer to your original question as to what the BCM does, it is a computer module under the dash that is involved in:

1. Door locks
2. Lighting
3. Horn
4. Anti theft
5. Keyless entry
6. Warning systems
7. Transmission
8. IPC

George