Heated Oxygen Sensor (Ho2S)
- If HO2S circuit is open or shorted, a Diagnostic Trouble Code (DTC) should set. See appropriate 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. Refer to the HO2S SIGNAL WIRE IDENTIFICATION
table.
- 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 HO2S HEATER WIRE IDENTIFICATION
table. 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.
HO2S SIGNAL WIRE IDENTIFICATION
| Application |
Wire Color |
| HO2S No. 1 |
Gray/Light Blue |
| HO2S No. 2 |
Red/Black |
| HO2S No. 3 |
Red/Light Green |
HO2S HEATER WIRE IDENTIFICATION
| Application |
Wire Colors |
| HO2S No. 1 |
Light Blue/Orange & Red/White |
| HO2S No. 2 |
Light Blue/Orange & Yellow/Light Blue |
| HO2S No. 3 |
Light Blue/Orange & White/Black |