Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the HO2S 1.
- Ignition ON, test for 2.5-3.5 volts between the high signal circuit terminal 1 and ground.
- If less than the specified range, test the high signal circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the ECM.
- If greater than the specified range, test the high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Test for 2-3 volts between the low signal circuit terminal 5 and ground
- If less than the specified range, test the low signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- If greater than the specified range, test the low signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Connect a test lamp between the input pump current circuit terminal 6 and B+. Verify the test lamp does not illuminate.
- If the test lamp illuminates, test the input pump circuit and pump current circuit for a short to ground. If the circuit tests normal, replace the ECM.
- Verify that the following conditions do not exist:
- Lean fuel injectors-Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 .
- Incorrect fuel system pressure-Refer to Fuel System Diagnosis .
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) .
- Exhaust leaks near the HO2S
- Engine vacuum leaks
- If you find any of the above conditions, repair as necessary.
- If all circuits test normal, replace the HO2S 1.
IMPORTANT:
The input pumping current circuit and the pump current circuit are connected internally within the ECM. If there is a condition with one of the circuits, the other circuit will be affected.