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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 year experience.
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CAM ONLY I have a 2005 GMC Sierra 2500hd Duramax with an

Customer Question

I have a 2005 GMC Sierra 2500hd Duramax with an intermittent ABS light. The ABS light started at the the same time I discovered a leak in the hydroboost line (supply I think, engine side or inside line) from the power steering pump to the hydroboost unit.
The hydroboost line was replaced, power steering was flushed and bleed. The intermittent ABS light is still an issue. Generally at low speed turns to the left most of the time, infrequently at low speed turns to the right and driving straight. The situation will generally improve after the vehicle is driven. There are no power steering or brake fluid leaks, with brake pressure applied on engine start the pedal drops and returns, steering is normal and braking in normal except infrequently you can feel the pedal drop and pulsate like the ABS is doing its deal for no reason and if you brake hard enough to engage the abs the vehicle pulls to the right. Thanks
Submitted: 1 year ago.
Category: GMC
Expert:  Gm Tech (Cam) replied 1 year ago.

Hi there, Thanks for requesting me. With your truck, I hear the abs is on but at times its off and the Abs activates?

If so, have you had a chance to get the codes?

Expert:  Gm Tech (Cam) replied 1 year ago.

Also have you had a chance to check for a loose front wheel bearing?

Customer: replied 1 year ago.
The abs lights illuminates with audio tone intermittently and has progressively gotten worse. The brakes seem to work properly to include abs functionality except occasionally the abs activated during normal braking and the vehicle will pull to the right. I have not checked codes, recently moved and diagnostic code reader is packed. Upper ball joints need to be replaced. Forgot to mention that I thoroughly cleaned the abs ground under the drivers side door and cleaned every abs quick disconnect with electrical contact cleaner. I have not cleaned and reseated the abs sensors. The abs light illuminates with almost every left hand turn, usually at lower speed with greater steering wheel movement. Right hand turns are 50% or less regular ding abs illumination. Unless coincidental, this all started at the same time my hydroboost lines failed which has been replaced as mentioned above.
Expert:  Gm Tech (Cam) replied 1 year ago.

Ok, everything your mentioning is screaming either a wiring issue to the front wheel speed sensor, a bad wheel speed sensor or a wheel bearing in the front.

Expert:  Gm Tech (Cam) replied 1 year ago.

What I would do is take the connector off the top of the upper control arm, measure resistance over the 2 pins in the connector and see if changes when you move the wiring. IF so, change that sensor and if the bearing is loose, change the bearing.

Customer: replied 1 year ago.
Forgot to mention when bleeding the power steering, the abs light illuminate every time turning the wheel to the left just before reaching the turn stop with the tires off the groun and only intermittently when turning to the right. While driving the abs light is consistent with larger steering wheel movement generally at lower speed. Don't believe speed is the issue, seems more like steering wheel movement but not sure.
Expert:  Gm Tech (Cam) replied 1 year ago.

That screams wiring to the sensor. IT is not related to the power steering. Check the wiring to the sensor as I mentioned and I think you will find it.

Customer: replied 1 year ago.
Check the resistance of the two pins going to the sensor on the wheel or to the wiring harness into the truck
Expert:  Gm Tech (Cam) replied 1 year ago.

bearing assembly.

Customer: replied 1 year ago.
Ok thanks. Will check it out. Think I got it. Disconnect the abs sensor at the frame and check resistance of the wires that runs down the upper control arm to the back of the hub.
Expert:  Gm Tech (Cam) replied 1 year ago.


Customer: replied 1 year ago.
Thanks. Will check it out tomorrow.
Expert:  Gm Tech (Cam) replied 1 year ago.

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