P0172

Diagnostic Chart:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) controls a closed loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The PCM monitors the heated oxygen sensor signal voltage and adjusts the fuel delivery based on the signal voltage while in closed loop. A change made to the fuel delivery changes the Long and Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the Heated Oxygen Sensor (HO2S) signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to trends in Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to fueling in order to re-center and restore control to Short Term Fuel Trim. You can use a scan tool in order to monitor the Short and Long Term Fuel Trim. The ideal fuel trim values are around 0 percent. A positive Fuel Trim value indicates that the PCM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the PCM is reducing the amount of fuel in order to compensate for a rich condition. If the PCM detects an excessively Rich or Lean condition, the PCM sets a DTC. The long term fuel trim diagnostic parameter is an average of several of the long term speed load learn cells which the PCM selects based on the engine speed and the engine load.

CONDITIONS FOR RUNNING THE DTC
^ No TP sensor, MAP sensor, MAF sensor, HO2S, KS sensor, Idle speed, Injector, Misfire, EGR Flow, CMP sensor DTCs are set.
^ EGR Flow test is inactive.
^ Engine coolant temperature between 20°C (68°F) and 115°C (239°F).
^ Barometric pressure more than 75 kPa.
^ Mass air flow between 3-60 grams per second.
^ Manifold absolute pressure between 15-85 kPa.
^ Intake air temperature between -20°C (-4°F) and 100°C (212°F).
^ Engine speed between 500-4000 RPM.
^ Throttle angle less than 65 percent.
^ Vehicle speed less than 131 km/h (82 mph).

CONDITIONS FOR SETTING THE DTC
The PCM in not able to correct for a rich condition in cylinder bank 1.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using the scan tool Clear DTC Information function.

DIAGNOSTIC AIDS
If the condition is intermittent, refer to Intermittent Conditions in Symptoms. Intermittent Conditions

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. Freeze frame data will aid in locating a hard to find malfunction. For example, if the fault only occurs at high speed, this would be determined by monitoring the fuel trim cells. The freeze frame will also indicate how many miles ago the condition was present.
4. If DTC P0175 is also set indicates both banks are operating rich. Inspect items that would cause both banks to operate rich.