03

Diagnostic Chart:

Trouble Code Number
- Scan tool 03
- MIL 52

Fault Message
- Front Bank O2S Stays Above Center (Rich)

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

Range of Check
- During closed-loop control

Set Condition
- Rich condition is detected from the front bank healed oxygen sensor input.

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