Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: Verify that the engine is in good mechanical condition before continuing with this diagnostic.

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 ECM to calculate the air flow models is initially based on the MAP sensor at ignition ON. When the engine is running, the ECM 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 and Sprockets Replacement (LC9/LMG/LY2/LY5) or Timing Chain and Sprockets Replacement (LY6/L76/L92) for the correct timing.
- Worn piston rings-Refer to Engine Compression Test .