Circuit/System Testing
- Verify none of the following conditions exist:
- The air intake duct system for loose clamps, cracks, or other damage
- The air intake duct system for being collapsed or restricted
- The B75 mass airflow sensor is installed correctly.
- Restricted air filter
- Q38 throttle body for dirt, debris, and coking. Also, throttle body blade or shaft damage. Refer to Throttle Body Inspection and Cleaning
for further diagnosis.
- Splits, kinks, or improper connections at the vacuum hoses
- Missing, restricted, or leaking exhaust components-Refer to Symptoms - Engine Exhaust
.
- Vacuum leaks at the intake manifold and Q38 throttle body.
- If a condition exists, repair as necessary.
- Ignition ON, observe the diagnostic trouble code (DTC) information with a scan tool. Verify that DTC P0641, P0651, P0697, or P06A3 is not set.
- Determine the current vehicle testing altitude. Compare the MAP Sensor pressure parameter to the reading in the Altitude Versus Barometric Pressure
table. The MAP sensor pressure parameter should be within the specified range indicated in the table.
- Engine idling, observe the MAP Sensor kPa parameter. The reading should be between 26-52 kPa (3.8-7.5 psi).
- Use the scan tool snapshot function to take a snapshot of the engine data list while performing the actions listed below.
- Engine idling
- Increase the engine speed slowly to 3,000 RPM and then back to idle.
- Exit from the scan tool snapshot and review the data.
- Observe the MAF Sensor g/s parameter frame by frame with a scan tool. The MAF Sensor g/s parameter should change smoothly and gradually as the engine speed is increased and then returned to idle.
- If all conditions test normal, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical
.