DTC P0421 [LF]: Notes
DTC P0421 (LF) DETECTION CONDITION AND POSSIBLE CAUSE
| DTC P0421 |
Warm up catalyst system efficiency below threshold |
| DETECTION CONDITION |
- The PCM compares the number of A/F sensor and HO2S inversions for a predetermined time. The PCM monitors the number of inversions side performs while front side inverts for a specified number of times when the following monitoring conditions are met, the PCM detects the inversion ratio. If the inversion ratio is below threshold, the PCM determines that the catalyst has deteriorated.
MONITORING CONDITIONS
- Calculated TWC temperature: more than 400°C {752°F}
- Engine speed: 1,500-3,000 RPM
- LOAD: 15-48%
(at engine speed 2,000 RPM
)
Diagnostic support note
- This is an intermittent monitor (catalyst).
- The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
- PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.
- FREEZE FRAME DATA (Mode 2/Mode 12) is available.
- The DTC is stored in the PCM memory.
|
| POSSIBLE CAUSE |
- Exhaust gas leakage
- A/F sensor and/or HO2S looseness
- TWC deterioration or malfunction
- PCM malfunction
|