ABS/TC light comes on after a period of time

[sbagdon]

On our 2000 Silhouette, the ABS/TC light comes on, after a period of driving. How long it takes to come on appears to be a function of cold temp, and distance... the colder it is, the quicker it goes on. Above a certain temp it never comes on, below a certain temp it comes on almost immediately, with a temp/time/distance curve in between those temps.

Thoughts? Best I can come up with is a wheel hub sensor. Are ABS error codes stored in the ECU, readable by any ODB-II reader? Thanks!

[gmtech1]

Originally Posted by sbagdon

On our 2000 Silhouette, the ABS/TC light comes on, after a period of driving. How long it takes to come on appears to be a function of cold temp, and distance... the colder it is, the quicker it goes on. Above a certain temp it never comes on, below a certain temp it comes on almost immediately, with a temp/time/distance curve in between those temps.

Thoughts? Best I can come up with is a wheel hub sensor. Are ABS error codes stored in the ECU, readable by any ODB-II reader? Thanks!

You need to have the ABS codes read with a capable scanner. A basic OBD 2 scanner will only read ECM codes, not ABS codes. Get the codes read before you waste time and money throwing parts at it.

[Tech II]

I agree, with GMtech1.....need to have the codes read with an ABS scanner/reader.....once you know what wheel caused the problem, you can do an ohm check and an a/c check......but that only checks out when the problem is happening, not if intermittent......once you know what wheel is the problem, disconnect the harness from the sensor and shake it......if water comes out of the harness, water intrusion could cause you to replace the harness AND the sensor....

[sbagdon]

ABS/TC light went on full-time, when the spring hit. It'll go out after the starting the car, yet as soon as the wheels move, the light will come on. Presuming it's a hub sensor. Will have the code read by a local auto parts store this week, and report back on the status.

[sbagdon]

Local auto parts store had an OBD-II + ABS. They read the code as C1218... "Pump Motor Circuit Short to Voltage or Motor Ground Open".

Google says the best-case is that it's a corroded ground to the EBCM (Electronic Brake Control Modele), so clean and re-attach a good ground, and the issues goes away. Worst-case is the EBCM and/or BPMV (Break Pressure Modulator Valve) needs replacing.

Anyone ever have experience with this code on the GMs? Thanks!

[gmtech1]

Originally Posted by sbagdon

Local auto parts store had an OBD-II + ABS. They read the code as C1218... "Pump Motor Circuit Short to Voltage or Motor Ground Open".

Google says the best-case is that it's a corroded ground to the EBCM (Electronic Brake Control Modele), so clean and re-attach a good ground, and the issues goes away. Worst-case is the EBCM and/or BPMV (Break Pressure Modulator Valve) needs replacing.

Anyone ever have experience with this code on the GMs? Thanks!

Go ahead and clean the ground and hope for the best. The big problem with diagnosing this code is that the circuit that needs to be tested is between the BPMV and the EBCM, so you cant check it with the two connected to each other. If cleaning the ground fails, your best and cheapest bet is to get a used BPMV/EBCM assy from a salvage yard, usually about 200.00. Usually its a problem with the BPMV itself, but a new one will run nearly 1000.00 and you may still need the EBCM. I have had pretty good luck with the used ones, but you don't know if they are any good till you install them. So I guess the choice is up to you...

[sbagdon]

Originally Posted by gmtech1

Go ahead and clean the ground and hope for the best. The big problem with diagnosing this code is that the circuit that needs to be tested is between the BPMV and the EBCM, so you cant check it with the two connected to each other. If cleaning the ground fails, your best and cheapest bet is to get a used BPMV/EBCM assy from a salvage yard, usually about 200.00. Usually its a problem with the BPMV itself, but a new one will run nearly 1000.00 and you may still need the EBCM. I have had pretty good luck with the used ones, but you don't know if they are any good till you install them. So I guess the choice is up to you...

Will try the ground-clean tonight, depending on weather (weather.com says it'll stop right around evening commute).

Just picked up a '99 Permier parts-van, which was the driver to resurrect all these broken-item fixes (so I should have all the parts to fix just about every up-gripe on the van). On the '99, the TCS light is out on the dash (instrument panel was free of lights or messages, during test-run), yet the TCS switch little light is lit. Seem to remember that the TCS switch on my '00 has no light (yet will check now). Is it safe to presume the ABS is "functionaly" working on the '99?

Also, in reading other forums, appears that to replace the BPMV, you have to bleed the BPMV/lines using a service tool (motorized-bleeding?). Is that something a non-tech can do? Thx.

[gmtech1]

Originally Posted by sbagdon

Will try the ground-clean tonight, depending on weather (weather.com says it'll stop right around evening commute).

Just picked up a '99 Permier parts-van, which was the driver to resurrect all these broken-item fixes (so I should have all the parts to fix just about every up-gripe on the van). On the '99, the TCS light is out on the dash (instrument panel was free of lights or messages, during test-run), yet the TCS switch little light is lit. Seem to remember that the TCS switch on my '00 has no light (yet will check now). Is it safe to presume the ABS is "functionaly" working on the '99?

Also, in reading other forums, appears that to replace the BPMV, you have to bleed the BPMV/lines using a service tool (motorized-bleeding?). Is that something a non-tech can do? Thx.

If there were no lights or messages on, it's a good chance the unit is ok. As far as bleeding it...MOST of the time I only bleed the lines at the ABS unit. Sometimes I need to bleed at the wheels also. Occasionally a automated bleed with a scanner is needed. What I have also found is a ABS stop after bleeding the BPMV will purge air also and improve the pedal feel.