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Home >> Mazda >> 2000 >> MPV DX >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0146: Rear Ho2S, No Activity Detected >> Testing
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DTC P0146: Rear Ho2S, No Activity Detected: Testing

NOTE: Ensure freeze frame data has been recorded. Check for service bulletins and on-line information.
  1. Verify stored DTCs. If any other DTCs are present, repair first. If no other DTCs are present, go to next step.
  2. Verify if DTC P0146 is present in FREEZE FRAME PID data. If DTC is present, go to next step. If DTC is not present in FREEZE FRAME PID data, go to TROUBLE SHOOTING - NO CODES article.
  3. Start engine. Warm engine to operating temperature. Using scan tool, access PID/DATA MONITOR. Monitor RHO2S. Depress accelerator pedal to WOT and release to race engine. Repeat at least 10 times. Scan tool should display O2 sensor voltage greater than .55 volt at least once. If voltage is not as specified, go to next step. If voltage is as specified, go to step  5 .
  4. Check O2 sensor installation. If sensor is loose, tighten sensor and go to step  7 . If sensor is tight, check for exhaust leaks upstream from O2 sensor. If any leaks are found, repair as necessary and go to step  7 . If no leaks are found, check for open or short in wiring between suspect O2 sensor and PCM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem is found, repair as necessary. If no problem is found, replace O2 sensor. After repair, go to step  7 .
  5. Check cooling system for combustion gasses. If no combustion gasses are present, go to next step. If combustion gasses are present, repair leak as necessary. After repair, go to step  7 .
  6. Check engine compression. If compression is okay, go to next step. If compression is low, repair as necessary. After repair, go to next step.
  7. Reconnect all components. Turn ignition on. Erase DTC. See CLEARING CODES in SELF-DIAGNOSTICS - INTRODUCTION - MIATA, MILLENIA, MPV & PROTEGE article. Start engine. Warm to operating temperature. Raise engine speed to more than 1500 RPM for 95 seconds. Using scan tool, check DTCs. If DTC P0146 is not pending, go to next step. If DTC P0146 is pending, replace PCM. PCM is mounted to passenger floor, behind glove box. After repair, go to next step.
  8. Perform after repair procedure. See AFTER REPAIR PROCEDURE  . If no DTC is present, testing is complete. If any DTC is present, go to appropriate test for diagnosis and repair.
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