Intermittent warning lights

I've got a 2001 Blazer (4.3L v6, TrailBlazer model, 156K miles) with an intermittant warning light problem. First it was the airbag light: would come on if the vehicle was very cold, then go away within a few minutes. Now it's the ABS and E-brake lights (together) -- sometimes they come right away then go off in a few minutes, sometimes I can drive quite a way and they'll suddenly pop on, sometimes they don't come on for days. Same problem with the Service 4WD light. I have no clue. All of the above items appear to be functioning normally.

We replaced the e-brake shoes last week (they were shot) and that didn't have any impact on the problem.

I'm suspecting some sort of loose wiring harness behind the dash. Any ideas?

Possiable wiring and body coputer net work connection and ground.
Needs put on a air bag and ABS and transmission transfer case and body capable scanner when the lights come on even before you turn key off.
Check for all past and present and history codes in all computer systems.
Some ABS and SIR codes will self clear when ign is turned off.
Air bag system is usually seperate but ABS and transfer case/4WD may lead back to one problem.
Post back any code no and we will try to help you.
MT

Thanks, MT. I'll stop by my mechanic on my way home from work tomorrow and have him check the codes for me. I'll let you know what I find. No ABS/Brake lights the whole way home yesterday or this a.m. on the way in. Service 4WD popped on again about 2 miles from my office (I drive 26 miles each way to work). Ugh.

Let us know what they find.
Even thow sometimes there will be codes stored in computer memory.
Try to get the lights on and leave it running so they can catch it with light on.
Good Luck
MT

My mechanic came back with the following codes:

P0122 - TPS circuit low input
P1122 - TPS circuit intermittent low voltage
C0265 - EBCM relay circuit - open

Seems like the TPS issues should be straightforward enough to figure out (thanks to the Haynes manual), but we're not quite sure where to begin with the EBCM.

I was surprised that it didn't throw a code for the TCCM, since the Service 4WD light had been popping on and off.

My mechanic came back with the following codes:

P0122 - TPS circuit low input
P1122 - TPS circuit intermittent low voltage
C0265 - EBCM relay circuit - open

Seems like the TPS issues should be straightforward enough to figure out (thanks to the Haynes manual), but we're not quite sure where to begin with the EBCM.

I was surprised that it didn't throw a code for the TCCM, since the Service 4WD light had been popping on and off.


Are you sure about code no C0265?
It is not a good engine code.
OBD 11 codes shows P0265 as a N0. 2 injector circuit problem.
Fix the TPS codes and clear codes and see how it does and what codes come back.
If any comes back post back code no.
Clear code

I am sure about the C0625 code, definitely not a P0625.

My mechanic cleared all the codes last night. I had no brake warning lights of any kind last night or this a.m., but that darned Service 4WD light popped on again about half way to work.

We're going to hunt down the electrical gremlins tomorrow morning.

On Friday, we caught my truck in the act of displaying the "Service 4WD" light again and took it directly to the mechanic. It threw a 2725 (?) code indicating a problem with the 4WD switch. On Sunday, we took off the kick panel and inspected the TCCM -- no water damage, nothing loose, corroded, or otherwise a problem. The switch, however, is not functioning normally anymore. Planning to replace the switch.

We'll dig into the other problems this coming weekend. We're doing a general tune-up and will address the TPS issue then. Still not sure what to do about the EBCM relay error...

Have you cleared codes and checked for what comes back?
MT

When my mechanic checked the codes on Friday, the earlier ones that he had cleared had not returned; the only one was the TCCM code.

However, those pesky brake warning lights reappeared yesterday, so I would bet there's a code in there again for that.

Yes.
If the relay code or what ever has not come back do not worry about it.
Just deal with what codes come back.
On abs codes you need to check when the light first comes on before turning key off.
The hard codes will self clear when key is turned off.
Need to catch them in the act.
A few scanners will pick up past or memory codes.
Good Luck and let us know how it goes.
MT

Well, today we did the full tune-up and in the process checked the ground for the EBCM. It was terribly corroded. We cleaned it up (got rid of the rust, cleaned up the chasis where the ground attaches, replaced the bolt, coated the whole thing with dielectric grease), but the light came back again after being absent for the past couple of days. Tomorrow we're going to put it up on the jackstands and do a visual inspection of the ABS sensors on each wheel. Not sure what to do about that one beyond that, aside from bite the bullet and take it to the dealer.

I ordered up a new TP sensor and new 4WD switch (we determined the switch is bad), they should be here in the next day or two.

These things are maddening! :banghead:

On the other hand, after new cap/rotor, new plugs, Accel coil, beefed up wires, and a few holes in the ol' air box, the Blazer's running like a top again:grinyes: Now if we could just get rid of the electrical gremlins...