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DTC P0421, P0431 [AJ] (VIN: JMZ LW19J7*# 300001-, JM0 LW10J300 300001-301405, JM6 LW10J300 300001-, JM8 LW28J**# 300001-301513)

BME010200400204

## European (L.H.D.) Specs.

DTC P0421 DTC P0431 | Warm-up catalyst system (RH/LH) efficiency below threshold
--- | ---
DETECTION CONDITION | • PCM compares the number of HO2S (Front) and HO2S (Rear) inversions for a predetermined time. PCM monitors the number of inversions the rear side performs while the front side inverts for a specified number of times when the following monitoring conditions are met. PCM detects the inversion ratio. If inversion ratio is below threshold, PCM determined that catalyst system has deteriorated. MONITORING CONDITION

  - Engine speed 1,340- 2,000 rpm
  - Calculated load 19.5- 44% (*1)
  - Vehicle speed 39.5- 96.0 km/h {24.5- 59.5 mph}
  *1: Maximum calculated load value varies depends on engine speed.

Diagnostic support note
• This is an intermittent monitor. (CATALYST)
• MIL illuminates if PCM detects the above malfunction conditions in two consecutive drive cycles.
• 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 | • WU-TWC deterioration or malfunction • Exhaust gas leakage • Looseness of HO2S (Front) • Looseness of HO2S (Rear) • 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 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. • Is other DTCs present? | Yes | Go to the applicable DTC inspection. (See DTC TABLE [AJ] (VIN: JMZ LW19J7*# 300001-, JM0 LW10J300 300001-301405, JM6 LW10J300 300001-, JM8 LW28J**# 300001-301513).)
No | Go to the next step.
4 | INSPECT EXHAUST SYSTEM FOR GAS LEAKAGE • Visually inspect exhaust system for exhaust gas leakage. • Is there any gas leakage? | Yes | Repair or replace the malfunctioning 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 oxygen sensors. • Is it normal? | Yes | Go to the next step.
No | Retighten sensor, then go to Step 7.
6 | INSPECT FRONT HO2S VOLTAGE • Access O2S11 for P0421 or O2S21 for P0431 PID using WDS or equivalent. • Verify PID while racing engine (in PARK or NEUTRAL). • Is PID reading normal? - Above 0.45 V when suddenly depress the accelerator pedal (rich condition).

- Below 0.45 V just after release the accelerator pedal (lean condition)

Yes
Replace the WU-TWC, then go to the next step.
No | Replace the sensor, then go to the next step.
7 | VERIFY TROUBLESHOOTING OF DTC P0421 OR P0431 COMPLETED • Make sure to reconnect all disconnected connectors. • Turn the ignition switch to the ON position (Engine off). • Clear the DTC from the PCM memory using the WDS or equivalent. • Run PCM adaptive memory procedure drive mode and HO2S heater, HO2S, and EGR system repair verification drive mode.
(See OBD DRIVE MODE [AJ] (VIN: JMZ LW19J7*# 300001-, JM0 LW10J300 300001-301405, JM6 LW10J300 300001-, JM8 LW28J**# 300001-301513).)
• Is the PENDING CODE of same DTC present?
Yes
Replace the PCM, then go to the next step.
No | Go to the next step.
8 | VERIFY AFTER REPAIR PROCEDURE • Perform "After Repair Procedure". (See AFTER REPAIR PROCEDURE [AJ].) • Is there any DTC present? | Yes | Go to the applicable DTC inspection. (See DTC TABLE [AJ] (VIN: JMZ LW19J7*# 300001-, JM0 LW10J300 300001-301405, JM6 LW10J300 300001-, JM8 LW28J**# 300001-301513).)
No | Troubleshooting completed.