U0121 possible fixes

Asked by Guru9JHMJD May 03, 2023 at 11:51 AM about the 2013 GMC Terrain SLT1

Question type: Maintenance & Repair

2013 GMC Terrain 15k miles barely ever driven brand-new condition kept in
garage no rust no corrosion no dirt immaculate. BRAKE ABS TRAC lights on,
Service Power Steering message, lane depart and collision alerts not
working 3 brand new fully charged tested-good batteries kept dying overnight
in 36 hours. Took to dealer DTC U0121 pulled ABS module fuse to stop
battery drain but told me it would cost $2000 to replace EBCM and
associated parts but even then wasn't sure it would solve the problem. Need
to know if there are any other possible causes, solutions, recommendations
for this nightmare. Never expected such a catastrophic problem from a car in
this new condition which isn't under warranty due only to time.

2 Answers

310,255

There is your problem, newer vehicles cannot just sit in a garage, they need driven at least once a week. Now the Terrain is a known problem vehicle, electronics and transmissions seem to be the two biggest problems. Now the next thing to do is get away from the dealer and have an independent shop check it over, I’ve seen a lot of ABS codes fixed by just cleaning up connectors and pulse rings and sensors. Also battery voltage is critical, if it drops too low it can cause all kinds electronic glitches.

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