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2012 GMC TERRAIN SLE 2.4
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Discussion Starter · #1 ·
Hello All:
I recently bought a 2012 Terrain 2.4 with 112k miles which hadn't been well taken care of. I took care of the usual problems, changed cam sensors, VVT solenoids and spark plugs, and now the engine is running smoothly, with no rough idle nor any check engine lights. However, the ABS, Stabilitrak lights and the accompanying chime, are driving me nuts! A few seconds after I start the SUV, these lights come on, but the brakes and power steering are functioning normally. I have a mid-grade scanner that reads the Electronic Brake Control (ABS) and power steering modules showing no codes on the ABS module, but on the Power Steering module there's a persistent U0121 (lost communication with EBCM) code. As soon as I clear it, it comes right back. The wheel sensors are working well, and the EBCM live data stream shows that all 4 of them are consistently reading the same speeds as the speedometer during a road test. According to various sites, this U0121 code can be caused by a bad EBCM ground, a corroded connector by the gas tank or a problem with the CAN wiring. Before I start dismantling everything and spending hours probing circuits, I was wondering if anyone had a similar issue and how they solved it. Any help would be greatly appreciated.
 

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'16 Equinox LTZ AWD 3.6
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I would check/ clean the ground and the rear connector first. Use a electronics cleaner / lubricant in the connector. That would be very suspect if you're in a salt zone, coastal or a rainy area.
 
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2012 GMC TERRAIN SLE 2.4
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Discussion Starter · #5 ·
I would check/ clean the ground and the rear connector first. Use a electronics cleaner / lubricant in the connector. That would be very suspect if you're in a salt zone, coastal or a rainy area.
Definitely! I will have access to a car lift tomorrow and plan on checking both of those. Will post the results.
 

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I was looking for a separate power steering module, but there doesn't appear to be one. Do you know if there's one and if so, where it's located?
From GM:
The electronic power steering control module is part of the power steering assist motor assembly.
It is paired with the steering gear's sensors.
 
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Discussion Starter · #8 ·
Definitely! I will have access to a car lift tomorrow and plan on checking both of those. Will post the results.
UPDATE; I cleaned and reseated the ground cable on the passenger's side of the engine compartment, and also inspected and cleaned the connector by the left side of the fuel tank. They were both pretty good to begin with (no corrosion under the SUV) and now are squeaky clean. I also inspected and cleaned the connector at the EPSM (power steering module) which was clean and undamaged. After all this, the problem still persists, the ABS/Stabilitrak/Brake light all come on shortly after starting the vehicle. I can clear the lights with my scanner, but they come back on after 30 seconds.
My scanner is not the best, and does not support bi-directional testing. However, I can communicate with the ABS module and see that all wheel sensors are working well and showing the same speed as the digital speedo reading on the dash while driving on the road. The system voltage read 14 volts, but the ABS motor voltage is 0. Also the solenoids are not activated. I am guessing that there's a CAN communication failure between the EBCM (ABS Module) and the ECM/PSCM, causing the Stabilitrak to shut down. I'm not sure how to test this without GM software, so I will try a used ABS module from the salvage yard first, then post the results.
🙏 Any suggestions or ideas will be greatly appreciated. :geek:
 

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'16 Equinox LTZ AWD 3.6
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Here's a link to a Malibu forum I am on. Fretting corrosion in connectors was common in GM vehicles in the 08 to 12 years. Connection can look clean but still have an issue affecting may of the systems, especially with the CAN system.
 
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