2021 GMC Sierra 1500: Engine light on truck wont start
Common wear/failure (not a recall)
Symptoms
Owners of the 2021 Sierra 1500 report: engine light on truck wont start. CarComplaints.com lists 1 owner complaints, average mileage 700 miles.
NHTSA has 362 owner complaints for the 2021 Sierra 1500 in this area. Examples:
- NHTSA complaint ODI #11771467 (filed 10/15/2026): “The contact owns a 2021 gmc sierra. the contact stated that while driving at 60 mph, a reduced power mode warning message unexpectedly illuminated, and the vehicle unexpectedly entered limp mode. the contact stated that the temperature gauge indicated a high t…”
- NHTSA complaint ODI #11771106 (filed 10/14/2026): “1. what component or system failed or malfunctioned, and is it available for inspection upon request? the failure involves the nox emissions control system, specifically nox sensor #2 and the associated nox catalyst/dpf assembly. diagnostic trouble codes p11d5…”
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: none clearly reported. Check for open recalls and extended warranty coverage with a dealer before paying out of pocket.
DIY difficulty: Pro
Internal engine work (lifters, oil consumption, fuel dilution diagnosis) requires engine teardown or dealer software/tests. (Our assessment.)
Cost
No sourced cost range: get a written quote after diagnosis.
Typical parts (search links, no affiliate codes)
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