Engine Management

Scan Tool 65 (MIL 21):

Trouble Code Number
- Scan tool 65
- General scan tool P0154
- MIL 21

Fault Message
- Front Bank Upstream O2S Stays at Center

Background
- Sensor output voltage is checked.
- If voltage stays at center instead of switching, an open circuit is likely.

Range of Check
- 2 or more minutes after starting engine
- Engine coolant temperature: More than 80°C (176°F) or more.

Set Condition
- Neither rich nor lean condition is detected from the front bank upstream heated oxygen sensor input. (Voltage is 0.5 volts for 1.5 minutes)

Probable Cause
- Heated oxygen sensor failed
- Wiring harness and connectors failed
- PCM failed