The PCM monitors the fuel trim values during predetermined driving enable conditions. If the average long term or short term fuel trims exceed the determined limit over a certain period of time, PCM sets P0171 DTC.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Monitor the fuel trim value | 1. Air leakage 2. Improper fuel pressure 3. PCV valve stuck 4. Restricted injector |
Enable Conditions |
•
Engine at operating temperature
•
Drive at a steady speed over 5 minutes (Vehicle speed less than 130km/h (80 mph))
•
Engine coolant temperature between 60°C (140°F) and 115°C (239°F)
•
No disabling faults (DTCs related to HO2S, purge valve, catalyst ) | |
Threshold value |
•
Average of short term fuel trim greater than 0.8 and Average of long term fuel trim greater than 1.2 | |
Diagnosis Time |
•
Continuous | |
MIL On Condition |
•
3 Driving Cycles |
