2006 SV6 ABS/Traction Lights

[rhb3]

Hi and thanks for reading...

I have 2 lights (ABS and Traction Control Disable) that I can not seem to reset. I've searched the forums but thus far have been unsuccessful and below is an overview:

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SYMPTOM:
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The two lights are on when I drive. At start, in park with the brake pedal pressed I am able to control the traction feature as designed with the traction disable light toggling as I enable and disable the system and the ABS light OFF. Next I start the van (typically I leave the traction control enabled...light OFF) and both lights are OFF until the very instant I take my foot off of the brake pedal at which time both the traction disable and ABS lights are ON. Note, if I merely leave the key in the on position and remove my foot from the brake pedal both lights stay OFF and will not come on. I should also note that I receive 3x DIC messages: "Service ABS System", "Service Traction System" and "Service Stability System".

WHAT I'VE DONE SO FAR:
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1) I tried reading codes with an Actron CP9180. No luck. I'll admit that I'm not proficient with this tool but I see no ABS/Traction info, etc. Both the Read codes and Read Pending codes come back PASS.

2) Based on a post and the fact that the lights activate as soon as I toggle the brake lights by releasing the brake pedal I checked rear lamps and swapped the top/bottom bulb on each side. All function appears normal including 3rd brake light. I see no sign of over current on the black wire as suggested in other pontiac threads.

3) I reseated all 4x brake sensor connectors. I didn't really notice any connectivity/continuity issues.

4) I raised each wheel to check for any play indicating wheel bearing. The front, drive wheel is a bit suspicious but not much play.

QUESTIONS:
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a) Is there a way to read the ABS codes with my scan tool or another? AutoZone wouldn't read this for me...I guess that's for emissions only!
b) Is there a flashing light method to determine ABS issue if any?
c) Is there a resistance and/or voltage check method for the sensors?
d) I'm leaning to the problem beings an ABS sensor and traction by default is disabled, agree?
e) Any ideas about the stability system message? That one baffles me.
f) Should I try to disconnect the battery...full reset, etc.?

Any insight and suggestions are welcome!

Thanks,
Rich

[dewaynep]

You probably have one bad abs sensor or bad wiring to one of the sensors. If you could get your local shop to scan the ABS for you they could tell you right away where the problem is. You can test each sensor by disconnecting it and putting a voltmeter across the 2 terminals. I believe the output should be over 600 millivolts A/C when spinning the tire/wheel (don't quote me on that voltage). In my experience measuring output of ABS sensors with a voltmeter is sketchy at best since you have to try to compare readings from one side to the other. The best method is with a scan tool so you can see if/when the sensor is dropping out. It is also possible to have a sensor that is shorted to ground or is an open circuit (since your problem occurs without even moving this is probably the case). Those are easy enough to check with an ohm meter. Like I said, it really is easiest to get it on an ABS capable scanner and see what it tells you.

[rhb3]

Additional Information for each sensor:

Wheel: Resistance(Ohms) Spin-Voltage(max Vac in mV) Supply-Voltage(Vdc)
Driver Rear: 1033 Ohms 233mV 1.71V
Driver Front: 1050 Ohms 179mV 1.72V
Pass Rear: 1036 Ohms 240mV 1.71V
Pass Front: 1047 Ohms 165mV 1.7V

Resistance was measured with wheel not moving and cold; i.e., the car sat overnight.

Spin Voltage was measured by turning as fast as possible by hand.

I'm curious about the supply voltage...1.7V. Does that sound right?

[dewaynep]

Since they are all basically the same, did you check to see if any of them is shorted to ground?

[rhb3]

No....darn it! I'll give that a go.

[rhb3]

No shorts from any wheel. I checked each terminal at each wheel to a local ground.

[dewaynep]

Well, I think we are right back to the start, you need to get it on an ABS capable scanner and see what the code is that is tripping the light. You said you checked all of the brake lights correct? I would double check the connectors at the taillight circuit boards. Other than that, you will need to get it scanned to really see what the problem is...

[rhb327]

The codes are C0120 and C0115.

The mechanic tried putting dielectric on the EBCM connector but still have the issue. The diagnosis is that the EBCM has failed (part #15873163). What bothers me is that it failed during a spin event in the snow where the traction control was enabled (light OFF). What's to prevent this from happening again? Should traction control be disabled whenever you drive in the snow (sounds counter intuitive)?

Thanks.

[dewaynep]

If the diagnosis is correct, that the EBCM has failed, I think you will be living without ABS or traction control. It is possible to have the EBCM rebuilt, but either proposition is an expensive one.