DTC Advanced Diagnostics: P0171 (3.0L Engine)
DTC P0171: Rear Bank (Bank 1) Fuel System Too Lean
General Description
The fuel system is monitored by the values of the air/fuel ratio feedback, the rear air/fuel ratio (A/F) sensor (bank 1, sensor 1), and the target air/fuel ratio. The value used for detecting malfunction is calculated by the following formula.
Long term fuel trim + (plus) short term fuel trim + (plus) (rear A/F sensor (bank 1, sensor 1) value - (minus) target air/fuel ratio)
If the value calculated from the formula above is a specified value, the powertrain control module (PCM) detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous* |
| Sequence | None |
| Duration | 10 minutes or more |
| DTC Type | Two drive cycles, MIL on |
*: The malfunction judgment is cleared when it is judged as normal under the same driving conditions in which the malfunction is detected.
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| BARO value [Baro Sensor] | 75 kPa (563 mmHg, 22.2 inHg) | - |
| Fuel feedback | Closed loop | |
[ ]: HDS Parameter
Malfunction Threshold
The value calculated from the following formula is 25 % or more for at least 0.5 second, and the condition are counted 1, 200 times.
Long term fuel trim + (plus) short term fuel trim + (plus) (rear A/F sensor (bank 1, sensor 1) value - (minus) target air/fuel ratio)
Possible Cause
- Rear A/F sensor (bank 1, sensor 1) failure
- Fuel pump failure
- Injector failure
- Fuel pressure regulator failure
- Fuel line failure
- Fuel supply system failure
- Mass airflow (MAF) sensor range/performance problem
- Manifold absolute pressure (MAP) sensor range/performance problem
- Vacuum hose misinstalled
- Throttle body air leak
- Intake manifold air leak
- Evaporative emission (EVAP) canister purge valve failure
Confirmation Procedure
Operating Condition
- Start the engine. Hold the engine speed [Engine Speed] at 3, 000 rpm without load (in P or N) until the radiator fan comes on.
- Drive at a steady speed between 15 - 75 mph (25 - 120 km/h) for at least 10 minutes.
- When freeze data is stored, drive the vehicle under those conditions instead of Driving Pattern step 2.
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.
Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive drive cycles in which the engine conditions are similar to the first time the malfunction was detected. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.