Fuel Trim Diagnostic Codes

A Fuel Trim diagnostic code will set when Fuel Trim values exceed programmed limits due to either "Rich" or "Lean" operating conditions. The "Long Term" or "Short Term" Fuel Trim numbers stored in the "Freeze Frame" data will indicate if the PCM was increasing or decreasing fuel delivery when the code was set.

A PCM that is increasing fuel delivery (to compensate for a "Lean" condition) will have a positive (+) "Long Term" Fuel Trim number. A PCM that is decreasing fuel delivery (to compensate for a "Rich" condition) will have a negative (-) "Long Term" Fuel Trim number.