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DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

DTC DETECTING CONDITION:


• Two consecutive driving cycles with fault

• GENERAL DESCRIPTION


TROUBLE SYMPTOM:


• Engine stalls.

• Idle mixture is out of specifications.


Important

After repair or replacement of faulty parts, conduct Clear Memory Mode and Inspection Mode .


WIRING DIAGRAM:


CHECK ANY OTHER DTC ON DISPLAY.

Is any other DTC displayed?

Yes

• Inspect the relevant DTC using “List of Diagnostic Trouble Code (DTC)”.

•
Note

In this case, it is not necessary to inspect DTC P0420.



No


CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR.

Turn the ignition switch to OFF.

Disconnect the connector from rear oxygen sensor and oxygen sensor.

Measure the resistance in harness between rear oxygen sensor and ECM connector.

Connector & terminal

(B19) No. 4 — (B135) No. 19:

(B19) No.1 — (B137) No. 13:

(B19) No.3 — (B135) No. 17:

Is the resistance less than 1 Ω?

Yes


No

Repair open circuit in harness between rear oxygen sensor and ECM.


CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR.

Measure the resistance between ECM connector and chassis ground.

Connector & terminal

(B135) No. 26 — Chassis ground:

Is the resistance less than 5 Ω?

Yes


No

Repair open circuit in harness between rear oxygen sensor and ECM.


CHECK EXHAUST SYSTEM.

Check for gas leaks or air suction caused by loose or dislocated nuts and bolts, and open hole at exhaust pipes.

Note

Check the following positions.

• Between cylinder head and front exhaust pipe

• Between front exhaust pipe and front catalytic converter

• Between front catalytic converter and rear catalytic converter


Is there a fault in exhaust system?

Yes

Repair or replace the exhaust system.


No


CHECK REAR CATALYTIC CONVERTER.

Separate the rear catalytic converter from rear exhaust pipe.

Is there damage at rear face of rear catalyst?

Yes

Replace the front catalytic converter. and rear catalytic converter


No


CHECK FRONT CATALYTIC CONVERTER.

Remove the front catalytic converter.

Is there damage at rear face or front face of front catalyst?

Yes

Replace the front catalytic converter.


No

Contact Service Center.