Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Sonoma, 2003 GMC Safari, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.

Fuel contamination, such as water and alcohol, will affect fuel trim.
A malfunctioning MAF sensor can cause a rich condition and set this DTC. See DTC P0101: MASS AIRFLOW SENSOR PERFORMANCE .
Using a scan tool, review the Failure Records. If an intermittent condition is suspected, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.