Heated Oxygen Sensor (Ho2S)
- If HO2S circuit is open or shorted, a Diagnostic Trouble Code (DTC) should set. See TESTS W/CODES
article. If any DTCs are present, repair as necessary. If no DTCs are present, go to next step.
- To check HO2S, warm engine to operating temperature, then turn off ignition. Disconnect connector from HO2S to be checked. Connect DVOM between ground and HO2S signal terminal. See Fig 1
.
- Start engine and run at high and low speeds while monitoring voltage. Voltage should fluctuate between .2-1.0 volt when accelerating and decelerating. If voltage is not as specified, replace HO2S.
- To check HO2S heater, disconnect connector from HO2S to be checked. Using ohmmeter, measure resistance between HO2S heater terminals AT HO2S connector. See Fig 1
. With HO2S at 68°F (20°C), resistance should be 2-5 ohms. With HO2S warm to hot, resistance should be 5-30 ohms. If resistance is not as specified, replace HO2S.
Courtesy of FORD MOTOR CO.