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Home >> Mazda >> 2000 >> MPV ES >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0138: Right Rear Ho2S, Input High Or DTC P0158: Left Rear Ho2S, Input High >> Testing
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DTC P0138: Right Rear Ho2S, Input High Or DTC P0158: Left Rear Ho2S, Input High: Testing

NOTE: Ensure freeze frame data has been recorded. Check for service bulletins and on-line information.
  1. Verify pending and stored DTCs. If any other DTCs are present, diagnose and repair first. If no other DTCs are present, go to next step.
  2. Verify if DTC P0138 or P0158 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. Turn ignition off. Disconnect suspect O2 sensor connector. Turn ignition on. Check voltage between appropriate O2 sensor harness connector terminal and ground. See REAR O2 SENSOR CIRCUIT IDENTIFICATION  table. If no voltage is present, go to next step. If voltage is present, repair short to power on appropriate circuit. Go to step  5 .
  4. Reconnect O2 sensor. Start engine. Using scan tool, access PID/DATA MONITOR. Monitor RHO2SR (P0138) or LHO2SR (P0158). Depress accelerator pedal to WOT and release to race engine. Repeat 10 times. Scan tool should display O2 sensor voltage greater than .45 volt during rich condition and less than .45 volt during lean condition. If voltage is as specified, go to next step. If voltage is more than .45 volt at all times, replace O2 sensor and go to next step.
  5. Reconnect all components. Turn ignition on. Erase DTC. See CLEARING CODES in SELF-DIAGNOSTICS - INTRODUCTION - MIATA, MILLENIA, MPV & PROTEGE article. Conduct Drive Modes No. 1 and No. 3 under DRIVE CYCLE PROCEDURE. See SELF-DIAGNOSTICS - INTRODUCTION - MIATA, MILLENIA, MPV & PROTEGE article. Using scan tool, check for DTCs P0138 and P0158. If DTC P0138 and P0158 are not pending, go to next step. If DTC P0138 or P0158 is pending, replace PCM. PCM is mounted to passenger floor, behind glove box. After repair, go to next step.
  6. 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.
REAR O2 SENSOR CIRCUIT IDENTIFICATION

O2 Sensor O2 Sensor Terminal PCM Terminal No.
Left "C" 61
Right "A" 35
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