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Diagnosis & Repair

  1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on and then turn hand-held tester or scan tool on.
  2. Using hand-held tester or scan tool, read intake air temperature for IAT sensor. If displayed intake air temperature is -40°F (-40°C), go to next step. If displayed intake air temperature is 284°F (140°C) or more, go to step  8. If displayed intake air temperature is the same as actual air intake temperature, problem is intermittent. Check for defective connections or intermittent problem in wiring between MAF meter and ECM. MAF meter is bolted to air intake hose, near air cleaner assembly and contains a Black 5-pin electrical connector. ECM is located behind glove box. See Figure.
  3. Turn ignition off. Disconnect electrical connector at MAF meter. MAF meter is bolted to air intake hose, near air cleaner assembly and contains a Black 5-pin electrical connector. Connect jumper wire between terminals No. 4 (Yellow/Green wire) and No. 5 (Blue/Black wire) on electrical connector for MAF meter. See Figure.
  4. Turn ignition on. Using hand-held tester or scan tool, read intake air temperature for IAT sensor. If displayed intake air temperature is less than 284°F (140°C), go to next step. If displayed intake air temperature is 284°F (140°C) or more, check for defective electrical connections at MAF meter and electrical connector. If electrical connections are defective, repair as necessary. If electrical connections are okay, replace MAF meter.
  5. Turn ignition off. Remove jumper wire. Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Ensure electrical connectors at ECM are securely installed so all terminals in electrical connectors are contacting terminals in ECM.
  6. Ensure electrical connector at MAF meter is still disconnected. Connect jumper wire between terminals No. 11 (Blue/Black wire) and No. 13 (Yellow/Green wire) at ECM electrical connector E9 with all electrical connectors installed on ECM. See Figure. This is the E2 and THA terminals on ECM.
  7. Turn ignition on. Using hand-held tester or scan tool, read intake air temperature for IAT sensor. If displayed intake air temperature is 284°F (140°C) or more, repair open Blue/Black wire or Yellow/Green wire between MAF meter and ECM. See WIRING DIAGRAMS article. If displayed intake air temperature is not 284°F (140°C) or more, replace ECM.
  8. Turn ignition off. Disconnect electrical connector at MAF meter. MAF meter is bolted to air intake hose, near air cleaner assembly and contains a Black 5-pin electrical connector. Turn ignition on. Using hand-held tester or scan tool, read intake air temperature for IAT sensor. If displayed intake air temperature is not -40°F (-40°C), go to next step. If displayed intake air temperature is -40°F (-40°C), replace MAF meter.
  9. Turn ignition off. Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Disconnect ECM electrical connector E9. See Figure. Ensure electrical connector is still disconnected at MAF meter.
  10. Turn ignition on. Using hand-held tester or scan tool, read intake air temperature for IAT sensor. If displayed intake air temperature is -40°F (-40°C), repair short in wiring harness and electrical connectors between MAF meter and ECM. See WIRING DIAGRAMS article. If displayed intake air temperature is not -40°F (-40°C), replace ECM.
    Fig 1: Locating Splice I20
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