• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provide an overview of each diagnostic category. |
The engine control module (ECM) controls a Closed Loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The ECM monitors the heated oxygen sensor (HO2S) 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 HO2S signal voltages. These changes fine tune the engine fueling. The long term fuel trim values change in response to trends in the 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. The ideal fuel trim values are around 0 percent. A positive fuel trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition. The fuel trim cells are based on the engine speed and load.
• | DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0133, P0222, P0223, P0300, P0335, P0336, P0337, P0341, P0342, P0400, P0404, P0405, P0406, P0444, P0445, P0510, P1320, P1321, P1402, P1403, P1511, P1512, or P1513 are not set. |
• | The engine is operating. |
• | The fuel system is in Closed Loop. |
• | The engine coolant temperature is greater 20°C (68°F). |
• | The evaporative emission (EVAP) canister is not saturated. |
• | The DTCs run continuously when the above conditions are met. |
The average short term fuel trim cell values are more than 30 percent for 5 minutes.
The average short term fuel trim cell values are less than -30 percent for 5 minutes.
DTC P0171 and P0172 are Type B DTCs.
DTC P0171 and P0172 are Type B DTCs.
• | The system will become lean if a fuel injector is not supplying enough fuel - P0171. |
• | A lean condition could be present during high fuel demand due to a fuel pump that does not deliver enough fuel, a plugged fuel filter, or a restricted fuel pipe - P0171. |
• | The system will become rich if a fuel injector is supplying too much fuel - P0172. |
• | Review the Freeze Frame/Failure Records with a scan tool. |
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
⇒ | If the MAP sensor pressure is not within the range specified for your altitude, refer to DTC P0107 or P0108 . |
⇒ | If greater than 10 percent, refer to DTC P0122, P0123, P0222, or P0223 . |
⇒ | If out of the specified range, refer to DTC P0131 or P0138, and DTC P0133 . |
• | Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
• | Splits, kinks, or improper connections at the vacuum hoses |
• | The fuel system is operating lean or rich. Refer to Fuel System Diagnosis . |
• | The fuel injectors are operating lean or rich. Refer to Fuel Injector Balance Test with Special Tool . |
• | Missing, restricted, or leaking exhaust components--Refer to Symptoms - Engine Exhaust . |
• | Vacuum leaks at the intake manifold, throttle body, and injector O-rings - P0171 |
• | Leaking crankcase ventilation system - P0171 |
• | The air intake duct for being collapsed or restricted possibly by a restricted air filter - P0172 |
• | Restricted air cleaner element - P0172 |
• | Leaking fuel pressure regulator--Inspect for evidence of fuel in the vacuum line. Refer to Fuel System Diagnosis - P0172. |
• | Excessive fuel in the crankcase - P0172 |
• | The incorrect operation of the EVAP control system - P0172 |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.