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HOMESERVICE MANUALSSUZUKI2013SX4 CROSSOVER, AUTOMATIC CVT TRANSREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE GENERAL INFORMATION & DIAGNOSISDIAGNOSTIC INFORMATION AND PROCEDURESDTC P0420: CATALYST SYSTEM EFFICIENCY BELOW THRESHOLDDTC TROUBLESHOOTING
2013 Suzuki SX4 Crossover, Automatic CVT Trans

DTC Troubleshooting

2013 Suzuki SX4 Crossover, Automatic CVT TransSECTION DTC Troubleshooting
DIAGNOSTIC INFORMATION AND PROCEDURES REFERENCE CHART

Step Action YES NO
1  Was "Engine and Emission Control System Check" performed?  Go to Step 2. Go to ENGINE AND EMISSION CONTROL SYSTEM CHECK .
2  DTC check 
  1. Check DTC.

Is there DTC(s) other than P0420? 		 Go to troubleshooting for applicable DTC. Go to Step 3.
3  Exhaust system visual inspection 
  1. Check exhaust system for leak, damage and looseness.

Is it in good condition? 		 Go to Step 4. Repair or replace defective parts.
4  HO2S circuit check 
  1. Check signal and ground circuits of HO2S for high resistance according to step 3 under DTC P0137/P0138 .

Are they in good condition? 		 Go to Step 5. Repair or replace defective wire harness.
5  A/F sensor signal circuit check 
  1. Check A/F sensor signal circuit according to Step 3 under DTC P0131/P0132/P0134/P2237 .

Are they in good condition? 		 Go to Step 6. Repair or replace defective wire.
6 
  1. Replace exhaust manifold (built in TWC). Refer to EXHAUST MANIFOLD REMOVAL AND INSTALLATION .
  2. Perform DTC confirmation procedure.

Is DTC P0420 still detected? 		 Go to Step 7. End.
7 
  1. Replace HO2S. Refer to HEATED OXYGEN SENSOR (HO2S) REMOVAL AND INSTALLATION .
  2. Check DTC.

Is DTC P0420 still detected? 		 Go to Step 8. End.
8 
  1. Replace A/F sensor. Refer to AIR FUEL RATIO (A/F) SENSOR REMOVAL AND INSTALLATION .
  2. Check DTC.

Is DTC P0420 still detected? 		 Substitute a known-good ECM and recheck DTC. Refer to DTC CHECK . End.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.