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Home >> Suzuki >> 2003 >> Aerio GS, AWD, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnosis & Repair Procedure
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Diagnosis & Repair Procedure

NOTE: For better performance and results of this diagnostic procedure, usage of appropriate wiring diagram is recommended. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
NOTE: Perform all voltage and resistance tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use an ohmmeter to isolate wiring harness shorts or opens.
  1. If engine system check has been performed, go to next step. If engine system check has not been performed, perform TEST D: ENGINE SYSTEM CHECK  under SYSTEM TESTS, then go to next step.
  2. Perform exhaust system visual inspection (leaks, damage and loose connection). If exhaust system is okay, go to next step. If exhaust system is faulty, repair as necessary and repeat DTC CONFIRMATION TEST .
  3. Check output voltage of HO2S-2 referring to DTC P0137 OR DTC P0138 . If diagnostic procedure results are okay, replace TWC. After repair, repeat DTC CONFIRMATION TEST . If diagnostic procedure results are faulty, repair as necessary and repeat DTC CONFIRMATION TEST .
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