P0174

DTC P0174 Fuel Trim System Lean Bank2





Circuit Description
In order to provide the best possible combination of driveability, fuel economy, and emission control, the vehicle uses a Closed Loop air and fuel metering system. While in a Closed Loop, the VCM monitors the oxygen sensor signal voltage. The VCM adjusts the fuel delivery based on a signal voltage. The long and short term fuel values, which a scan tool can monitor, indicates a change made to the fuel delivery Ideal fuel trim values are around 128; if the oxygen sensor signal indicates a lean condition, the VCM adds fuel. This results in fuel trim values above 128. If the oxygen sensor detects a rich condition, the fuel trim values will read below 128. This indicates that the VCM is reducing the amount of fuel delivered. If an excessively lean condition is detected, the VCM sets this DTC.

Conditions for Setting the DTC
- No IAC or idle DTCs
- No HO2S sensor DTCs
- No TP sensor DTCs
- No MAP sensor DTCs
- No EGR sensor DTCs
- No EVAP sensor DTCs No ECT sensor DTCs
- No MAF sensor DTCs
- No IAT sensor DTCs
- No AS sensor DTCs
- No System Voltage DTCs
- No Misfire DTCs
- Throttle position less than 69.9%
- Engine speed is between 575-4000 RPM
- The BARO greater than 70 kPa
- The ECT is between 75-114°C (167-237°F)
- The MAP is between 22-85 kPa.
- The IAT is between -8.25-76°C (4-169°F)
- The MAF is between 3-85 g/s
- The vehicle speed less than 85 mph

Action Taken When the DTC Sets











Important: To complete a trip cycle for the fuel trim diagnostic, the fuel trim diagnostic test must enable and run according to the current DTC Will Set When criteria above. A trip is not considered complete until the fuel trim diagnostic has run by the VCM.