Circuit/System Verification
IMPORTANT:
Verify that the engine is in good mechanical condition before continuing with this diagnostic.
- With the ignition ON and the engine OFF, and while observing the TP Sensor parameter, press the accelerator pedal slowly until the throttle is in the wide open position. Release the accelerator pedal slowly until the throttle is returned to the closed position. If the TP sensor does not increase steadily to more than 98 percent, or does not decrease steadily to less than 1 percent, refer to DTC P0121 .
- Verify the integrity of the air induction system by inspecting for the following conditions:
- Any damaged components
- Loose or improper installation
- Improperly routed vacuum hoses
- Any vacuum leak
- Any type of restriction
- MAP sensor seal that is missing or damaged
- Verify that restrictions do not exist in the MAP sensor vacuum source.
- Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust .
- A skewed or stuck engine coolant temperature (ECT) or IAT sensor will cause the calculated models to be inaccurate and may cause this DTC to run when it should not. Refer to Temperature Versus Resistance .
- The BARO that is used by the PCM to calculate the air flow models is initially based on the MAP sensor at ignition ON. When the engine is running, the PCM will continually update the BARO value near wide open throttle using the MAP sensor and a calculation. A skewed MAP sensor will cause the BARO value to be inaccurate. Use the scan tool and compare the BARO parameter at ignition ON to the Altitude vs. Barometric Pressure Table. Refer to Altitude Versus Barometric Pressure .
- A skewed MAP sensor will also cause the first and second intake manifold models to disagree with the actual MAP sensor measurements. Use the scan tool and compare the MAP Sensor parameter to a known good vehicle, under various operating conditions.
- Inspect for the following conditions:
- Incorrect Cam timing-Refer to Timing Chain, Sprockets, and/or Tensioner Replacement for the correct timing.
- Worn piston rings-Refer to Engine Compression Test .