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Home >> Mazda >> 2021 >> CX-5 Sport, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 24 (On-Board Diagnostic - Engine Control (VIN Y) (2 Of 3)) >> DTC P0421-00: Catalytic Converter System >> Troubleshooting Diagnostic Procedure >> Intention of troubleshooting procedure

Intention of troubleshooting procedure

WARNING: This page is about a different variant/trim than selected.
TROUBLESHOOTING DIAGNOSTIC PROCEDURE

STEP INSPECTION RESULTS ACTION
1 PURPOSE: INSPECT INSTALLATION OF HO2S
  • Inspect installation of HO2S.
  • Is the HO2S installed securely?
Yes Go to the next step.
No Retighten the HO2S, then go to Step 8.
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [VIN Y] .)
2 PURPOSE: INSPECT INSTALLATION OF A/F SENSOR
  • Inspect installation of A/F sensor.
  • Is the A/F sensor installed securely?
Yes Replace the A/F sensor and/or HO2S, then go to Step 8.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [VIN Y] .)
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [VIN Y] .)
No Retighten the A/F sensor, then go to Step 8.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [VIN Y] .)
3 PURPOSE: INSPECT INSTALLATION OF HO2S
  • Inspect installation of HO2S.
  • Is the HO2S installed securely?
Yes Go to the next step.
No Retighten the HO2S, then go to Step 8.
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [VIN Y] .)
4 PURPOSE: INSPECT INSTALLATION OF A/F SENSOR
  • Inspect installation of A/F sensor.
  • Is the A/F sensor installed securely?
Yes Go to the next step.
No Retighten the A/F sensor, then go to Step 8.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [VIN Y] .)
5 PURPOSE: INSPECT EXHAUST SYSTEM FOR LEAKAGE
  • Visually inspect for exhaust gas leakage from the exhaust system.
  • Is there any malfunction?
Yes Repair or replace the malfunctioning part according to the inspection results, then go to Step 8.
No Go to the next step.
6 PURPOSE: VERIFY IF OTHER DTCs ARE DISPLAYED
  • Reconnect all disconnected connectors.
  • Clear the DTC from the PCM memory using the M-MDS. (See CLEARING DTC .)
  • Implement the repeatability verification procedure. (See Repeatability Verification Procedure .)
  • Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure. (See ON-BOARD DIAGNOSTIC TEST .)
  • Are any other PENDING CODEs and/or DTCs present?
Yes Go to the applicable PENDING CODE or DTC inspection.
(See DTC TABLE .)
Go to the next step.
No Go to the next step.
7 PURPOSE: VERIFY CATALYTIC CONVERTER (WU-TWC) MALFUNCTION
Yes Replace the catalytic converter (WU-TWC), then go to the next step.
(See EXHAUST SYSTEM REMOVAL/INSTALLATION [VIN Y] .)
No DTC troubleshooting completed.
8 PURPOSE: VERIFICATION OF VEHICLE REPAIR COMPLETION
  • Always reconnect all disconnected connectors.
  • Clear the DTC from the PCM memory using the M-MDS. (See CLEARING DTC .)
  • Implement the repeatability verification procedure. (See Repeatability Verification Procedure .)
  • Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure. (See ON-BOARD DIAGNOSTIC TEST .)
  • Is the same Pending DTC present?
Yes Repeat the inspection from Step 1.
Go to the next step.
No Go to the next step.
9 PURPOSE: VERIFY IF THERE IS ANY OTHER MALFUNCTION
  • Is any other DTC or pending code stored?
Yes Go to the applicable DTC inspection.
(See DTC TABLE .)
No DTC troubleshooting completed.