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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 125 (Engine Control System Self Diagnostics (2UZ-FE)) >> Diagnostic Tests >> DTC P0136: Heated Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2) &/Or DTC P0156: Heated Oxygen Sensor Circuit (Bank 2 Sensor 2) >> Diagnosis & Repair

Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
  1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTCs P0136 and/or P0156 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
  2. Check for open and short in wiring harness and electrical connectors between HO2S and ECM. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article. HO2S is located on exhaust pipe, behind catalytic converter. ECM is located behind glove box. See Figure. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
  3. With hand-held tester or scan tool still connected to DLC3, start engine and warm engine to normal operating temperature. Monitor HO2S output voltage while quickly accelerating engine to 4000 RPM 3 consecutive times. Output voltage should fluctuate from 0.40 volt or less to 0.50 volt or more. If output voltage is within specification, go to step  8. If output voltage is not within specification, go to next step.
  4. Turn ignition off. Disconnect HO2S 4-pin connector. See Figure & Figure . Measure resistance between HO2S 4-pin connector terminals No. 2 (+B) and No. 1 (HT). Make note of measurement. Then, measure resistance between HO2S 4-pin connector terminals No. 1 (HT) and No. 4 (E1). See HO2S HEATER RESISTANCE SPECIFICATIONS . If resistance is within specification, go to next step. If resistance is not within specification, replace HO2S. See HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  5. Remove EFI relay from engine room relay box. See Figure. Test relay. See EFI RELAY under MODULES, MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. If relay is bad, replace it. If relay is Ok, reinstall relay and go to next step.
  6. Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Check continuity between ECM and HO2S connectors at terminals listed below. See Figure and Figure .
    • ECM 35-pin connector E5 terminal No. 5 (HT1B) and HO2S (Bank 1 Sensor 2) terminal No. 1. Continuity should exist.
    • ECM 35-pin connector E5 terminal No. 29 (OX1B) and HO2S (Bank 1 Sensor 2) terminal No. 3. Continuity should exist.
    • ECM 35-pin connector E5 terminal No. 25 (HT2B) and HO2S (Bank 2 Sensor 2) terminal No. 1. Continuity should exist.
    • ECM 35-pin connector E5 terminal No. 21 (OX2B) and HO2S (Bank 2 Sensor 2) terminal No. 3. Continuity should exist.
    • ECM 35-pin connector E5 terminal No. 5 (HT1B) and body ground. Continuity should not exist.
    • ECM 35-pin connector E5 terminal No. 29 (OX1B) and body ground. Continuity should not exist.
    • ECM 35-pin connector E5 terminal No. 25 (HT2B) and body ground. Continuity should not exist.
    • ECM 35-pin connector E5 terminal No. 21 (OX2B) and body ground. Continuity should not exist.
  7. If continuity is as specified, replace HO2S. See HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article. If continuity is not as specified, repair wiring as necessary. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.
  8. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Perform test drive confirmation and then go to next step. See TEST DRIVE CONFIRMATION .
  9. Recheck for DTCs. If DTCs P0136 and/or P0156 does not exist, go to next step. If DTCs P0136 and/or P0156 exists, replace HO2S. See HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  10. Verify if vehicle ran out of fuel. If vehicle ran out of fuel, DTCs P0136 and/or P0156 was caused by the vehicle running out of fuel. If vehicle did not run out of fuel, problem is intermittent. Check for defective connections or intermittent problem in wiring. ECM is located behind glove box. See Figure.
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