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DTC Troubleshooting

DIAGNOSIS PROCEDURE

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  Exhaust system visual inspection 
  1. Check exhaust system for leaks, damage and loose connection.

Is it in good condition? 		 Go to Step 3. Repair or replace.
3  HO2S-2 output voltage check 
  1. Check output voltage of HO2S-2 referring to DTC P0137 / P0138: O2 SENSOR CIRCUIT LOW / HIGH VOLTAGE (SENSOR-2) (FOR VEHICLE WITH ORVR)  or DTC P0137 / P0138: O2 SENSOR CIRCUIT LOW / HIGH VOLTAGE (SENSOR-2) (FOR VEHICLE WITHOUT ORVR) .

Is check result satisfactory? 		 Replace both catalyst case and exhaust pipe No.1 with new ones. Check "WHT" and "ORN" wires for open and short, and connections for poor connection.
If wires and connections are OK, replace HO2S-2.
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