04

Diagnostic Chart:

Trouble Code Number
- Scan tool 04
- MIL 51

Fault Message
- Front Bank O2S Stays Below Center (Lean)

Background
- Sensor output voltage is checked.
- It voltage stays below center instead of switching, a fault in the circuit is likely.

Range of Check
- During closed-loop control

Set Condition
- Lean condition is detected from the front bank heated oxygen sensor input.

Probable Cause
- Heated oxygen sensor failed
- Sensor signal circuit open
- PCM failed