2018 / ECLIPSE CROSS / EC - Workshop Manual
13 -FUEL > 13A-DIRECT INJECTION AND MULTIPOINT FUEL INJECTION (DI AND MPI) > TROUBLESHOOTING > DIAGNOSIS CODE PROCEDURES > CODE NO. P0421 CATALYST MALFUNCTION
Code No. P0421: Catalyst Malfunction
FUNCTION
- The signal from the oxygen sensor (rear) differs from the linear A/F sensor. That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the linear A/F sensor becomes similar to the oxygen sensor (rear).
- The engine-ECU compares the output of the linear A/F sensor signal and the oxygen sensor (rear) signal.
TROUBLE JUDGEMENT
Check Conditions
- Engine speed is less than 3,000 r/min.
- The accelerator pedal is open.
- Air flow sensor output is more than 6.4 g/sec and is less than 50 g/sec.
- More than 3 seconds have elapsed after the above mentioned three conditions have been met.
- Under the closed loop air/fuel ratio control.
- Vehicle speed is more than 1.5 km/h.
- The engine-ECU monitors for this condition for 5 cycles of 10 seconds each during the drive cycle.
- Short-term fuel trim is more than -25% and is less than +25%.
Judgement Criterion
- When the monitoring for 10 seconds is carried out 5 times, the frequency ratio of oxygen sensor (rear) and linear A/F sensor is more than 0.85.
FAIL-SAFE AND BACKUP FUNCTION
PROBABLE CAUSES
- Deteriorated catalytic converter
- Failed engine-ECU
DIAGNOSIS PROCEDURE
STEP 1. Replace the exhaust front pipe (integrated with catalytic converter).
- After replacing the exhaust front pipe (integrated with catalytic converter), reconfirm whether the diagnosis code is set.
Is the diagnosis code set?
Replace the engine-ECU.
Check end.
