Emergency brake light and ABS lights come on

[kiesurfer805]

I have a 2002 LB7 with 220K miles with Ca emissions. Looking for a little help on a brake problem. The brake light and ABS light will just go on. Once they come on they will stay on until the engine is turned off. Both lights come on together and it doesn't usually do it at start up, it usually happens while driving. Intermittent problem doesn't always happen.

Could it be as simple as changing out the relay?

Could it be the brake pads are worn, I haven't checked them but the brakes work just fine.

Has anybody else had this problem?

[DmaxMaverick]

Check first, the front wheel bearings. Jack up one corner and push/pull at the TOP of the tire (not like you are trying to "steer", but in/out at the top). Repeat on the other side. Any movement indicates a bad bearing, and probably the cause of at least one alarm. Check the brake pads while you're in there. Less than about 1/8" is nearing time for replacement.

[kiesurfer805]

Ok I finally got the time to check it out.

No wheel bearing play at all.

Brakes have lots of pad left, I measured them at .345"

[tx dave]

Did you ever find out what was causing the lights to come on. My 2001 has started doing the same thing when I start up. Not all the time but when it does I turn it off and restart and they go away.

[letsgo]

the ABS sensor CAN become contaminated with steel, rust, particals, that will cause an incorrect data count rather than an equal count, OBD2 should diagnose the problem and if you had electrical schematics you can disconnect the sensors and take meter readings. (you need instructions to do this)
good luck , drive safe

[Heartbeat Hauler]

I just dealt with this a few months ago and it isn't purty. Unless, you are one of the lucky ones. Underneath the drivers door, under the truck on a cross brace for the frame you will find the ground wire for the Electronic Brake Control Module (EBCM). Make sure that is clean, remove the wires, wire-brush the frame area and clean everything, wires, bolt everything, then reassemble. This takes like 15 minutes. Some of the ABS issues can be caused by grounding OR connections to the module. Also make sure the connectors on the EBCM are seated properly, remove and clean and plug them back in. The unit is located under the truck on the inside frame rail beneath the driver's seat area.

Also, does your ABS light come on at start up, or after you have been driving? If it is there at start up you may have some type of connection problem. Mine would clear after a couple of start cycles, but then would return after driving or applying the brakes. Mine turned out to be the EBCM unit and valve.....$2200 at the dealership... I will say that the dealership spent a lot of time checking ALL of the connections (at no cost to me) to make sure that it was the EBCM.

You can save a ton of money if you order the parts from a place like GMPARTSDIRECT. Even if you let the dealership do the install the savings on parts will just about pay for the labor. There is a huge markup on these parts from GM. If you can do this work yourself, then you can save about 400 bucks in labor. Good luck.

[Heartbeat Hauler]

the ABS sensor CAN become contaminated with steel, rust, particals, that will cause an incorrect data count rather than an equal count, OBD2 should diagnose the problem and if you had electrical schematics you can disconnect the sensors and take meter readings. (you need instructions to do this)
good luck , drive safe

This is a good point. The ABS sensor in the wheel hub can become contaminated. The crud and rust can build up between the sensor and the seating area of the hub which will eventually push the sensor up away from the pickup-point (think of the gap in a spark plug becoming too wide to spark across) which will send out an error and then the ABS light/Brake light on the dash. The sensor can be removed and cleaned (hub area too) if you are carefull, but the sensor is made of plastic and it is very easy to break or crack it. If you try this it might be worth it to have a spare on hand. If you get it scanned I think Tech II can tell you which side it is....if this is the problem.

[Heartbeat Hauler]

Oh, I forgot one of the easy things to check. It is common that the ABS sensor wire (which is visible if you remove the tire) rubs against the suspension parts, rubbing through the insulation causing an error then the ABS and Brake light. Also, if you follow that wire up you will see the connector, make sure that is seated properly. I can't think of anything else right now...

[Inspector]

How about brake fluid level?
Denny