Circuit/System Verification
WARNING: This page is about a different car, the 2007 Pontiac G5 Pursuit, 2007 Pontiac G5, and 2007 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
- If DTC P0641 or P0651 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Verify the integrity of the entire air induction system by inspecting for the following conditions:
- Any damaged components
- Loose or improper installation
- An air flow restriction
- Any vacuum leak
- Water intrusion
- In cold climates, inspect for any snow or ice buildup
- Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust .
- Engine running, observe the scan tool MAF Sensor parameter. The reading should be between 1,700-3,200 Hz depending on the ECT.
- A wide open throttle (WOT) acceleration from a stop should cause the MAF Sensor parameter on the scan tool to increase rapidly. This increase should be from 2-6 g/s at idle to greater than 100 g/s at the time of the 1-2 shift.
- The barometric pressure (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 WOT using the MAP sensor and a calculation. A skewed MAP sensor will cause the BARO value to be inaccurate. Determine the current vehicle testing altitude. Ignition ON, observe the scan tool BARO sensor parameter. Compare the parameter 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.