2021 GMC Sierra 2500HD: Check engine light on
Common wear/failure (not a recall)
Symptoms
Owners of the 2021 Sierra 2500HD report: check engine light on. CarComplaints.com lists 1 owner complaints, average mileage 100 miles.
NHTSA has 6 owner complaints for the 2021 Sierra 2500HD in this area. Examples:
- NHTSA complaint ODI #11686699 (filed 09/11/2025): “When i’m in reverse the up the cameras turn off. on one incident i was backing up and the camera turned off causing me to back up into the wall of my house…”
- NHTSA complaint ODI #11633825 (filed 01/03/2025): “Headlights and turn signals failed. flickering of various lights (daytime running lamp, low beam, high beam, turn signals) followed by total failure. 3700 dollar repair at dealer to replace both headlamp assemblies. barely over miles of warranty, but still …”
Likely causes
Sources do not establish a single root cause; diagnosis is needed. Owner-reported fixes are listed below.
Fix, in plain English
Most common owner-reported solutions on CarComplaints.com: they had to update the software (1 reports). Check for open recalls and extended warranty coverage with a dealer before paying out of pocket.
DIY difficulty: Moderate
Finding and splicing chewed wiring is doable with a multimeter and patience but can be time-consuming; harness replacement is pro work. (Our assessment.)
Cost
No sourced cost range: get a written quote after diagnosis.
Typical parts (search links, no affiliate codes)
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