Fuel System Monitor

OBD System Description - Fuel System Monitor

Fuel System Description / Monitoring Procedure
As fuel system components age or otherwise change over the life of the vehicle, the adaptive fuel strategy learns deviations from stoichiometry while running in closed loop fuel. These learned corrections are stored in keep alive memory as long term fuel trim corrections. They may be stored continue to change beyond normal limits or if a malfunction occurs, the long term fuel trim values will reach a calibratable rich or lean limit where the adaptive fuel strategy is no longer allowed to compensate for additional fuel system changes. Long term fuel trim corrections at their limits, in conjunction with a calibratable deviation in short term fuel trim, indicate a rich or lean fuel system malfunction.

Post Catalyst Fuel Trim System Description / Monitoring Procedure
The system detects a malfunction of the fuel delivery system, including feedback control based on a secondary oxygen sensor, when the fuel delivery system is unable to maintain a vehicle's emissions at standards.

DTC Description / Detecting Condition / Confirmation Procedure

P0171, P0174
Refer to DTC P0171 / P0174: System Too Lean. P0171 P0174

P0172, P0175
Refer to DTC P0172 / P0175: System Too Rich. P0172 P0175

P2096, P2097
Refer to DTC P2096 / P2097: Post Catalyst Fuel Trim System Too Lean/Too Rich (Bank 1 Sensor-2).

P2098, P2099
Refer to DTC P2098 / P2099: Post Catalyst Fuel Trim System Too Lean/Too Rich (Bank 2 Sensor-2).

Operation Part 1:

Operation Part 2:

Fuel System Monitor