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Home › Mitsubishi › 1998 › Montero › Repair and Diagnosis › Engine Performance › System › Engine Controls - Tests W/Codes › DTC Tests › DTC P0431: Catalyst Efficiency Below Threshold

DTC P0431: Catalyst Efficiency Below Threshold

NOTE: This test applies to left bank diagnostics on 3.0L vehicles equipped with California emissions only. For terminal identification, see TERMINAL IDENTIFICATION . For circuit and wire color identification, see WIRING DIAGRAMS article.
  1. Check manifold and front pipe for cracks. Repair exhaust system as necessary. Go to step 7). If exhaust system is okay, go to next step.
  2. Using scan tool, read left rear Heated Oxygen Sensor (HO2S) voltage (item 69). With engine at normal operating temperature, vehicle in 2nd gear and at wide open throttle, voltage should be 0.6-1.0 volt. If voltage is as specified, go to next step. If voltage is not as specified, go to DTC P0156  test.
  3. Using scan tool, read left front Heated Oxygen Sensor (HO2S) voltage (item 39). With engine at wide open throttle, voltage should be 0.6-1.0 volt. If voltage is as specified, go to next step. If voltage is not as specified, go to DTC P0150  test.
  4. Using scan tool, read left front Heated Oxygen Sensor (HO2S) voltage (item 39). With engine at 2000 RPM, voltage should switch between 0-0.4 and 0.6-1.0 volt 15 times or more within 10 seconds. If voltage is as specified, go to next step. If voltage is not as specified, replace front HO2S. Go to step 7).
  5. Road test vehicle and attempt to duplicate conditions that caused original complaint. Recheck for DTCs. If DTC P0431 is displayed, replace catalytic converter. Go to next step. If no DTCs are displayed, test is complete.
  6. Road test vehicle and attempt to duplicate conditions that caused original complaint. Recheck for DTCs. If DTC P0431 is displayed, replace PCM. Go to next step. If no DTCs are displayed, test is complete.
  7. Road test vehicle and attempt to duplicate conditions that caused original complaint. Recheck for DTCs. If no DTCs are displayed, test is complete.
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