Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the appropriate HO2S.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal D and ground.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition circuit and replace as necessary.
- Ignition OFF, connect a test lamp between the heater control circuit terminal E and B+.
- Idle the engine, and verify the test lamp illuminates or flashes.
- If the test lamp is always OFF, test the heater control circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.
- Ignition ON, verify that the appropriate scan tool HO2S voltage parameter is between 350-500 mV.
- If less than the specified range, test the signal circuit terminal B for a short to ground. If the circuit/connections test normal, replace the ECM.
- If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit/connections test normal, replace the ECM.
- Connect a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool HO2S voltage parameter is less than 60 mV.
- If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.
- Connect a 3 A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool HO2S voltage parameter is less than 60 mV.
- If greater than the specified range, test the low reference circuit for an open/high resistance or for a short to voltage. If the circuit/connections test normal, replace the ECM.
- Verify that none of the following conditions exist:
- If you find any of the above conditions, repair as necessary.
- If all circuits/connections test normal, replace the appropriate HO2S 1.