My daughter has a 2001 Blazer with 200,000 miles and it runs great. But the brake light as well as the check engine light comes on and off just whenever. I have had it to the shop a few times and there is never a code and usually just resets after hook up and disconnect.
What gives?

 

Do the lights come on simultaneously?
Does the check engine light come on when the ignition is initially turned to the RUN position, and then shut off after the engine is running?

 

I never noticed what is on and what isn't when the ign. is turned to the on initially.
I do know they just come on while the engine is running, just random. They don't come on at the same time but random. Either one rarely stay on for more then a few min - a few hours. Then may not come on for a week or the next day.

 

You have cold solder joint problems inside the EBCM.I had the same problem.Took mine apart carefully and tried to repair myself but my solder gun was not up for the task so I brought it to my local T.V. repair man and he expertly evacuated/soldered the bad areas. If you are adventureous there are several you tubes on this repair and internet repair services.

 

[QUOTE=45Frank;653109]I never noticed what is on and what isn't when the ign. is turned to the on initially.
QUOTE]

We are here to try to help people who wish to help themselves. Are you looking to complete diagnosis and repairs yourself, or are you here because an unqualified shop is thowing up their hands at your problem and you don't know what to do? If it is only the latter, you simply need to find a better shop. If it is the former, we can help - but you need to go look and answer the Captain's question. This is the first true step of the diagnosis. It will tell us if the PCM is in control of the SES light. All other speculation at this point is just BS.

 

If you don't mind me asking, what did he charge you? I have had an ABS code of something like "right front wheel speed sensor irratic." I replaced that sensor and it didn't do anything. I'm thinking there's something bad in the wiring. I'm thinking of either A., doing what you did, or B., buying a new/used junkyard EBCM.

 

I bought an EBCM from a salvage yard for $75.00 and it was faulty,constant running. I then decided to repair mine. I carefully separated the module with a razor knife and after failing to do a proper repair on the six known problem points, I paid the T.V. repair shop $20.00 for an expert repair. Then I sealed the module with black RTV. P.S. You can drive without the EBCM you just won't have ABS. A Torx #9 is needed for disassembly. ECBM Rebuild At Home Fix ABS and Brake Light on - YouTube

 

[QUOTE=Lesmyer;653164]OK turn key on all lights come on. Start the engine
then randomly the brake light and the check engine lights come on then off, different times and random, stays on for a day, ten minutes or sometime just turning it off then restarting it and they go off, sometime they don't come on for weeks. The ABS light doesn't come on when running.

 

Not very likely the EBCM is causing the problem as it is not electronically involved with the check engine light. Could be two separate problems. One common denominator between the two, is possibly poor solder connections on the printed circuit board at the electrical connector for the instrument cluster. To test it, you'll need to remove the instrument cluster bezel to access the connector on the top of the instrument cluster. Then wiggle the connector with the engine running. If the problem shows up, the cluster needs to be removed and disassembled for access to the circuit board. There are 24 solder connections on the circuit board for the connector. The solder joints can be re-flowed using a low wattage soldering pencil, not a gun. If you need additional solder, use 60/40 lead/tin rosin core solder only.

 

[QUOTE=45Frank;653194]Captain has given you the instrument cluster as a possibility to check on, as it does not seem the two separate problems (2 different lights) would be related except at that point. So your next task is to remove the bezel and wiggle the IP cluster conector with the engine running and report results.

One thing I'm curious about from your answer above is if it is the ABS light or the parking brake light that is coming on.