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Discussion Starter · #1 ·
Each morning on cold start, our Terrain engages the ABS for the first 1-2 seconds of braking. Usually this is while backing out of the garage. Once it gets that out of its system, it is perfectly fine the rest of the day. Does not seem to be temperature dependent, at least not from 0-60F, it behaves the same.

No codes. No lights.

Any ideas in where to start? I am “guess” we most likely have a whee speed sensor failing….but I would assume that would give us trouble more often. I have a basic BT ODBII reader but it doesn’t appear to have enough smarts to see the ABS system nor wheel speed sensor info.


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How healthy is your battery? Just because it cranks up and starts doesn't mean it's in good shape.
After cold starting if battery is a little weak the rest of the modules onboard suffer from a ''brown out'' then after alternator gets a charge going things may return to normal.
Yes, a full spectrum scan of all 4 code families is needed and if no codes I would suspect the battery.
 

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Discussion Starter · #3 ·
In theory the battery is fine. It gets put on a charger monthly. It is driven daily 30+ minutes. I think the battery is around 3 years old. I have zero proof either way on the real condition.

Took it to the dealer for oil change and they said the rear brakes were below 2mm and that was the cause. Not sure I believe that is the cause but had them replace pads and rotors since I know it is too cold out for me to do it. We have just over 100k on these so not surprising they are worn and in need of replacement.

We shall see in the morning if it continues.


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2011 Equinox 1LT V6 3.0L FWD 182k miles
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My ABS does the same thing ... “chatters” every time I back out of my driveway at home or parking space at work. I usually just give it a stern tap to the brake pedal to stop it. Need to replace a front Hub (has a cracked Magnetic Ring on the backside and has thrown a Code for the sensor). I’ve had the new Hub since the past Spring or Summer and have taken at least two 900-mile one-way trips with it like this. I would doubt thin Brake Pads would cause the problem. You’re probably gonna start seeing Stabilitrak OFF with messages in the DIC and a Code for the Sensor on one of the Front Wheels. I know you said it’s too cold right now, but if you catch a warmer day, you might want to take a flashlight to the backside of the Hub and see if your Hub Magnetic Rings are still intact.
 
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Discussion Starter · #5 ·
Confirmed still doing it after rear brake replacement. I was able to cold start it tonight and as I rolled it out of the garage and down the driveway, at least 8 presses of the pedal triggered ABS.

I plugged in my new ODBII reader and the voltage from the battery is a tad suspect. With the car off, it was sitting at 12.3’ish initially which is what I expected it to be at. Step on the brake pedal and turn on the headlights we drop below 12V almost immediately.

When the car is started the voltage dips down into the 9V range then back up to 14’ish.

I have hooked up my charger to let it do it’s thing overnight and I will see how it is in the morning.

Note today was about 45F in the garage so not super cold but not warm. My wife is noting that when she remote starts the car to warm it up, it doesn’t do it. Soooo…if that is true, maybe it is the battery? Not enough data to be conclusive.

We drop back into the 20s tomorrow so I likely I will be crawling under the car anytime soon.


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Discussion Starter · #6 ·
Charger on overnight, showing charge cycle complete, and ABS still pulsed in the morning when backing out of garage. Only did it once which was an improvement, but just one data point.

I did not get a chance to watch battery voltage this morning.


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