Circuit/System Testing
- Ignition OFF and all systems OFF, it may take up to for 2 minutes for all vehicle systems to power down. Disconnect the harness connector at the B75C Multifunction Intake Air sensor.
- Test for less than 2Ω between the low reference circuit terminal 3 and ground.
- If 2Ω or greater
- Ignition OFF, disconnect the harness connector at the K20 engine Control Module.
- Test for less than 2Ω in the low reference circuit end to end.
- If 2Ω or greater, repair the open or high resistance in the circuit.
- If less than 2Ω replace the K20 engine Control Module.
- If less than 2Ω
- Ignition OFF, all vehicle systems OFF, test for less than 2Ω between the ground circuit terminal 7 and ground.
- If 2Ω or greater
- Ignition OFF, disconnect the harness connector at the K20 engine Control Module.
- Test for less than 2Ω in the ground circuit end to end.
- If 2Ω or greater, repair the open or high resistance in the circuit.
- If less than 2Ω, repair the open/high resistance in the ground connection.
- If less than 2Ω
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 and ground.
- If the test lamp does not illuminate and the circuit fuse is good
- Ignition OFF, remove the test lamp and remove the fuse for the ignition voltage circuit.
- Test for less than 2Ω in the ignition voltage circuit end to end.
- If 2Ω or greater, repair the open/high resistance in the circuit.
- If less than 2Ω, verify the fuse is not open and there is voltage at the fuse.
- If the test lamp does not illuminate and the circuit fuse is open
- Ignition OFF, remove the test lamp and remove the fuse for the ignition voltage circuit.
- Test for infinite resistance between the ignition voltage circuit and ground.
- If less than infinite resistance, repair the short to ground on the circuit.
- If infinite resistance, test all components connected to the ignition circuit, replace as necessary.
- If a test lamp illuminates
- Ignition ON, test for 4.8-5.2V between the humidity signal circuit terminal 8 and ground.
- If less than 4.8V
- Ignition OFF, disconnect the harness connector at the K20 engine Control Module.
- Test for infinite resistance between the signal circuit and ground.
- If less than infinite resistance, repair the short to ground on the circuit.
- If infinite resistance
- Test for less than 2Ω in the signal circuit end to end.
- If 2Ω or greater, repair the open/high resistance in the circuit.
- If less than 2Ω, replace the K20 engine Control Module.
- If greater than 5.2V
- Ignition OFF, disconnect the harness connector at the K20 engine Control Module.
- Ignition ON, test for less than 1V between the signal circuit and ground.
- If 1V or greater, repair the short to voltage on the circuit.
- If less than 1V, replace the K20 engine Control Module.
NOTE:If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.
- If between 4.8-5.2V
- Determine if EL-38522-A
Variable Signal Generator or equivalent is available.
- EL-38522-A, Variable Signal Generator; or equivalent is not available
- Test or replace the B75C Multifunction Intake Air sensor.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.
- Verify the DTC does not set.
- If the DTC sets
Replace the K20 engine Control Module.
- If the DTC does not set
- If the DTC sets
- All OK.
- EL-38522-A, Variable Signal Generator; or equivalent is available
- Ignition OFF, connect the leads of the EL-38522-A
Variable Signal Generator as follows:
- Red lead to the signal circuit terminal 8 at the harness connector
- Black leads to ground
- Battery voltage supply lead to B+
- Set the EL-38522-A
Variable Signal Generator to the following specifications.
- Signal switch to 5V
- Frequency switch to 250Hz
- Duty Cycle switch to 50% (Normal)
- Ignition ON, observe the scan tool Intake Air Humidity parameter. The scan tool parameter should be between 45-55%.
- If not between 45-55%.
Replace the K20 engine Control Module.
- If between 45-55%.
- If not between 45-55%.
- Test or replace the B75C Multifunction Intake Air sensor.