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DTC P0420 [L3]

BME010200400208

DTC P0420 | Catalyst system efficiency below threshold
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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
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1 | VERIFY FREEZE FRAME DATA HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded? | Yes | Go to the next step.
No | Record FREEZE FRAME DATA on repair order, then go to the 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 the next step.
No | Go to the next step.
3 | VERIFY RELATED PENDING CODE OR STORED DTCS • Turn the ignition switch off, then to the ON position (Engine off). • Verify related pending code or stored DTCs. • Are other DTCs present? | Yes | Go to appropriate DTC troubleshooting.
No | Go to the 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 the 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 the next step.
No | Retighten sensor, then go to Step 7.
6 | INSPECT TWC • Clear DTC using WDS or equivalent generic OBD function. • Cycle the ignition switch off then back to the ON position. • Inspect TWC.

  (See THREE-WAY CATALYTIC CONVERTER (TWC) INSPECTION [L3].)

• Is TWC normal?
Yes
Replace suspected oxygen sensor, then go to the next step.
No | Replace TWC, then go to the next step.
7 | VERIFY TROUBLESHOOTING OF DTC P0420 COMPLETED • Make sure to reconnect all disconnected connectors. • Turn the ignition switch to the ON position to ON (Engine off). • Clear DTC from memory using WDS or equivalent. • Run OBD DRIVE MODE.
(See OBD DRIVE MODE [L3].)
• Is PENDING CODE of same DTC present?
Yes
Replace PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION [L3].)
No | Go to the next step.
8 | VERIFY AFTER REPAIR PROCEDURE • Perform "After Repair Procedure". (See AFTER REPAIR PROCEDURE [L3].) • Is there any DTC present? | Yes | Go to the applicable DTC inspection. (See DTC TABLE [L3].)
No | Troubleshooting completed.