Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the B75B mass air flow/intake air temperature sensor.
- Ignition OFF, all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 Ω between the ground circuit terminal C 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 voltage circuit terminal B and ground.
- If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance.
- Ignition ON, test for 4.8-5.2 V between the MAF sensor signal circuit terminal A and ground.
- If less than the specified range, test the MAF sensor 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 MAF sensor signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
- Ignition OFF, connect the red lead of the J-38522
variable speed generator to the MAF sensor signal circuit terminal A at the harness connector. Connect the battery voltage supply to B+, and the black lead to ground.
- Set the J-38522
variable speed generator to the following specifications.
- Signal switch to 5 V
- Frequency switch to 5 KHz
- Duty Cycle switch to Normal
- Engine idling, observe the scan tool MAF Sensor parameter. The reading should be between 4, 950-5, 050 Hz.
- If not within the specified range, replace the K20 ECM.
- If all circuits test normal, test or replace the B75B mass air flow/intake air temperature sensor.