Cadillac DeVille Problem Report

Cadillac DeVille Smog Check Failure Due to Excessive Carbon Buildup

(7 reports)

Excessive carbon build up in the engine combustion chambers may be the cause of a smog check failure due to excess NOx emissions. A "top engine" decoarbonization cleaning procedure will commonly correct this concern.

Caddy failed due to NOx being too high on both high and low speed tests -
Car failed for high nox -
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