DTC P0420 [L3]

BME010200400W02

DTC P0420

Catalyst system efficiency below threshold

DETECTION CONDITION

• PCM compares number of front HO2S and rear HO2S inversions for a predetermined time. PCM monitors number of inversions rear side performs while front side inverts for a specified number of times when the following monitoring conditions are met. PCM detects inversion ratio. If inversion ratio is below threshold, PCM determines that catalyst system has deteriorated.
MONITORING CONDITION
- Engine speed 1,500- 3,000 rpm
- Calculated load 15- 48%(*1)
*1: Maximum calculated load value varies depending on engine speed.
Diagnostic support note
• This is a intermittent monitor. (CATALYST)
• MIL illuminates if PCM detects the above malfunction conditions in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
• DIAGNOSTIC MONITORING TEST RESULTS and PENDING CODE are stored if PCM detects the above malfunction condition during first drive cycle.
• FREEZE FRAME DATA is available.
• DTC is stored in the PCM memory.

POSSIBLE CAUSE

• TWC deterioration or malfunction
• Exhaust gas leakage
• Loose front HO2S
• Loose rear HO2S
• Front HO2S malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION

1
VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
• Has FREEZE FRAME DATA been recorded?
Yes
Go to next step.
No
Record FREEZE FRAME DATA on repair order, then go to next step.
2
VERIFY RELATED SERVICE INFORMATION AVAILABILITY
• Check for related Service Information availability.
• Is any related Service Information available?
Yes
Perform repair or diagnosis according to available Service Information.
• If vehicle is not repaired, go to next step.
No
Go to next step.
3
VERIFY RELATED PENDING CODE OR STORED DTCS
• Turn ignition key to OFF then ON (Engine OFF).
• Verify related pending code or stored DTCs.
• Are other DTCs present?
Yes
Go to appropriate DTC troubleshooting.
No
Go to next step.
4
INSPECT GAS LEAKAGE OF EXHAUST SYSTEM
• Visually inspect exhaust gas leakage in exhaust system.
• Is there any gas leakage?
Yes
Repair or replace faulty exhaust parts, then go to Step 7.
No
Go to next step.
5
INSPECT INSTALLATION OF FRONT AND REAR OXYGEN SENSORS
• Inspect for looseness of front and rear HO2S.
• Are they secure?
Yes
Go to next step.
No
Retighten sensor, then go to Step 7.
6
INSPECT TWC
• Clear DTC using WDS or equivalent generic OBD function.
• Cycle ignition key to OFF then back to ON.
• Inspect TWC.
(See THREE-WAY CATALYTIC CONVERTER (TWC) INSPECTION [L3].)
• Is TWC okay?
Yes
Replace suspected oxygen sensor, then go to next step.
No
Replace TWC, then go to next step.
7
VERIFY TROUBLESHOOTING OF DTC P0420 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Turn ignition key to ON (Engine OFF).
• Clear DTC from memory using WDS or equivalent.
• Run OBD DRIVE MODE.
• Is PENDING CODE of same DTC present?
Yes
Replace PCM, then go to next step.
No
Go to next step.
8
VERIFY AFTER REPAIR PROCEDURE
• Perform "After Repair Procedure".
• Is there any DTC present?
Yes
Go to applicable DTC troubleshooting.
No
Troubleshooting completed.