Emissions - DTC P0420 Diagnostic Information

FORENZA

Section Title: Engine
TSB No. TS 29 09071

Division: Automotive
Category: Technical

SUBJECT:
IMPROPER DIAGNOSIS OF CATALYTIC CONVERTER FAILURE WHEN
DTC P0420 IS PRESENT

MODEL(S):
FORENZA, FORENZA WAGON, RENO (RQ420)

YEAR:
2006~2008

CONDITION:
Catalytic Converters are being replaced unnecessarily under warranty and customer pay. When the warranty return Catalytic Converters are evaluated at A.S.M.C., the majority are passing the P0420 diagnostic test.

CAUSE:
Technicians must follow the comprehensive diagnostic process as outlined in the Suzuki Service Manuals.

CORRECTION
DO NOT replace the Catalytic Converter assembly purely based on the fact that the DTC P0420 is present, especially if there are additional codes stored. The P0420 Service Manual procedure, when followed, requires that a significant number of DTC's, when present, must be addressed and corrected prior to confirming the P0420 failure remains, and only then can it be properly diagnosed and tested.





PART(S) INFORMATION:

Keys to a successful diagnosis

1. Read and follow the Service Manual section for "DTC P0420: Catalyst System Low Efficiency". Please see the example attached from the 2006 Forenza/Reno Service Manual.





2. Familiarize yourself with the "Conditions for Setting the DTC" which must be met for the system to set the DTC (shown at the right").

3. Operate the vehicle within the "Conditions for Setting the DTC" and observe the Tech 2 scan tool to confirm the readiness test completes. If the test does not run or fails to complete, to improve the consistency and success of completing the readiness test, please follow the "road test" process outlined below to ensure that the required conditions are met. The idle conditions suggested will help reduce the occurrence of interruptions once the detection sequence begins.

4. If the Readiness Test for the Catalyst has been completed and there is no current or pending P0420 DIG stored, the catalytic converter is not defective and should not be replaced. If any DTC is set, correct and clear the code and repeat Step # 3.

5. If the P0420 DTC is stored continue on to item # 6 and proceed with further troubleshooting and diagnosis to determine the condition of the catalyst.





6. Ensure that all items called out in the "Test Description" section of the procedure are completed prior to beginning the "Troubleshooting" portion or the findings may be falsely influenced, resulting in an incorrect diagnosis.





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