Circuit/System Testing
- 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 leaks
- Water intrusion
- In cold climates, inspect for any snow or ice buildup
- Inspect the B75B MAF/IAT sensor element for contamination.
- Ignition OFF, disconnect the harness connector at the B75B MAF/IAT sensor.
- Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes, test for less than 5 Ω between the ground circuit terminal B and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
- Ignition ON, test for 4.8-5.2 V between the signal circuit terminal A and ground.
- If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
- If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
- Ignition OFF, connect the red lead of the EN-38522: Variable Signal Generator to the signal circuit terminal A at the B75B MAF/IAT sensor harness connector. Connect the battery voltage supply to the B+, and the black lead to ground.
- Set the EN-38522: Variable Signal Generator signal switch to 5 V, the Frequency switch to 5K, and the Duty Cycle switch to Normal.
- Engine idling, observe the scan tool MAF Sensor parameter. The scan tool MAF Sensor parameter should be between 4,950-5,050 Hz.
- If the MAF Sensor parameter is not within the specified range, replace the K20 ECM.
- If all other circuits test normal, test or replace the B75B MAF/IAT sensor.