Circuit/System Testing
- Verify that there are no contaminants, water, or too high of a concentration of ethanol in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis and the J 44175-A Instruction Manual.
- Ignition OFF, disconnect the harness connector at the B198 fuel composition sensor.
- Ignition OFF and 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 2 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 B+ circuit terminal 1 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the fuse is open, test all the components connected to the circuit, and repair or replace as necessary.
- Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 3 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 J 38522 Variable Signal Generator to the signal circuit terminal 3 at the B198 fuel composition sensor harness connector. Connect the battery voltage supply to B+, and the black lead to ground.
- Set the J 38522 Variable Signal Generator Signal to 5 V, the Frequency to 60 Hz, and the Duty Cycle to Normal.
- Ignition ON, verify the scan tool Fuel Composition Sensor parameter is at 60 Hz.
- If not at the specified value, replace the K20 ECM.
- If all circuits test normal, test or replace the B198 fuel composition sensor.