Fuel System Monitor
OBD System Description - Fuel System MonitorSystem 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.
DTC P0171 / P0172: System Too Lean / Rich.
DTC Detecting Condition:
DTC Detecting Condition and Trouble Area
DTC Confirmation Procedure
WARNING:
- When performing a road test, select a place where there is no traffic or possibility of a traffic accident and very careful during testing to avoid occurrence of an accident.
- Road test should be carried out with 2 persons, a driver and tester, on a level road.
NOTE: Check to make sure that the following conditions are satisfied when using this DTC Confirmation Procedure.
- Intake air temp.: between 10 °C and 60 °C (14 °F and 140 °F)
- Altitude (barometric pressure): 2500 m, 8202 ft or less (560 mmHg, 75 kPa or more)
1. With ignition switch turned OFF, connect scan tool.
2. Turn ON ignition switch and clear DTC using scan tool.
3. Start engine and warm up to normal operating temperature.
4. Increase vehicle speed till engine speed is higher than 1500 r/min.
5. Operate vehicle within freeze frame data condition as noted for 5 min.
6. Stop vehicle and check DTC and pending DTC.
Step 1 - 4:
Step 5 - 9:
DTC Troubleshooting
Operation:
Enable Condition Part 1:
Enable Condition Part 2:
Typical Malfunction Thresholds:
Fuel System Monitor