2000 Sonoma ABS lights

[Bill B]

The ABS and Brake warning lights come on at times.

When starting the truck in the morning the warning lights on the dash behave as you would expect, light momentarily then go off.
After reaching normal operating temperature, turn off engine then restart, the warning lights come on and stay on. (like a trip to the store for example).
Of course this doesn't happen all the time, some days the warning lights don't stay on.
The 4 wheel disc pads have been replaced, they were worn but still had life left. The emergency brake was adjusted but the pads were not replaced. The ABS system seems to operate correctly in that I can feel the pulsing when they activate on a slippery surface. (regardless of whether the warning lights are on or off)
This problem was occuring before brake pad replacement.
What tests can I perform to isolate the cause prior to a visit to the repair shop?

Bill

[84fiero123]

You can borrow an OBII reader at most parts stores and see if it’s throwing any codes.

It could just be that it needs brake pads.

[Cableguy]

You could disconnect battery see if that clears any silliness the computer is getting up too.

or put tape over lights and adjust radio volume accordingly



Sorry I'll stop...

[TrailLeadr]

You could disconnect battery see if that clears any silliness the computer is getting up too.

or put tape over lights and adjust radio volume accordingly



Sorry I'll stop...

Jamie, I can't believe you're making me say this...

I know the dealers charge a lot, but it's not worth it to ignore the light.
Either have the codes pulled, or take it in for service. It's not safe for your vehicle to be on the road while that light is on.
It doesn't matter if it works properly as far as you can tell. Something is amiss, and it should be taken care of ASAP.

I feel as though I say this too often, but ABS light doesn't mean it won't work when needed, it also means it could activate when not needed leaving you with nearly no braking power.

[Cableguy]

I'm sorry you know you really are right here. If codes are coming up from time to time only, does the computer store that to be read later by the reader. I've always wondered that? Even if light is out when being read?

[Bill B]

Jamie, I can't believe you're making me say this...

I know the dealers charge a lot, but it's not worth it to ignore the light.
Either have the codes pulled, or take it in for service. It's not safe for your vehicle to be on the road while that light is on.
It doesn't matter if it works properly as far as you can tell. Something is amiss, and it should be taken care of ASAP.

I feel as though I say this too often, but ABS light doesn't mean it won't work when needed, it also means it could activate when not needed leaving you with nearly no braking power.

Thank you all for your responses, I fully intend to take the truck in for service, but was thinking there must be routine checks that I could make to eliminate the "oh it was just a loose connection" kind of repair. The dealer's labor costs may be slightly higher than an independant shop but I think the dealer technicians have a higher experience level for a specific vehicle which could result in a lower labor cost overall.

Thanks again,
Bill

[Bill B]

You could disconnect battery see if that clears any silliness the computer is getting up too.

or put tape over lights and adjust radio volume accordingly



Sorry I'll stop...

I tried the tape route but the light is so bright I had to cover the whole instrument panel to prevent it from being a distaction. Now I don't see the lights but I keep getting speeding tickets cause I can't see the speedo......

[TrailLeadr]

I tried the tape route but the light is so bright I had to cover the whole instrument panel to prevent it from being a distaction. Now I don't see the lights but I keep getting speeding tickets cause I can't see the speedo......

LOL...not a good situation.

I know that on some of the vehicles with ABS, magnetic particles will gather around the end of the sensor. Your issue sounds like it has more to do with heat than anything else.

To help narrow it down, have you ever started the vehicle, and let it idle for a while so the engine compartment gets nice and warm, and then shut it off and see if it happens without the vehicle being moved.
This way you can see if the problem is at the control module, or if it's at the wheels, or a short in the line.

If it happens without the vehicle moving then it's something in the module, more than likely heat related.

If not, then it's probably either a short in the line, or heat at the wheels from the brakes affecting a bad sensor, or a sensor that's on it's way out.

[Cableguy]

LOL...not a good situation.

I know that on some of the vehicles with ABS, magnetic particles will gather around the end of the sensor. Your issue sounds like it has more to do with heat than anything else.

To help narrow it down, have you ever started the vehicle, and let it idle for a while so the engine compartment gets nice and warm, and then shut it off and see if it happens without the vehicle being moved.
This way you can see if the problem is at the control module, or if it's at the wheels, or a short in the line.

If it happens without the vehicle moving then it's something in the module, more than likely heat related.

If not, then it's probably either a short in the line, or heat at the wheels from the brakes affecting a bad sensor, or a sensor that's on it's way out.

Good advice! My question up top kinda got missed. Does the fault code get stored in ECM memory even if light is out on dash? At time you put reader on?
I guess that goes for my work van too Patrick?

[TrailLeadr]

Good advice! My question up top kinda got missed. Does the fault code get stored in ECM memory even if light is out on dash? At time you put reader on?
I guess that goes for my work van too Patrick?

Sorry, I thought you were thinking out loud.
I'm pretty sure they were not retained if the light went back out in OBDI. I'm guessing that was changed with OBDII, but I can't say for sure.
Sorry.