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DTC P1139: Front Ho2S No. 1 Heater Circuit Range/Performance Problem - IMPREZA 2.2L, Legacy & Outback 2.5L M/T & Outback Sport

  1. Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . Start and warm engine to normal operating temperature. Turn ignition off. Disconnect ECM connector B134 (35-pin connector) and front HO2S connector. Using an ohmmeter, measure resistance between ECM connector B134 (35-pin connector) terminal No. 22 and front HO2S connector terminal No. 4. See Figure and Figure . If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and front HO2S. See WIRING DIAGRAMS article.
  2. Measure resistance between ECM connector B136 (30-pin connector) terminal No. 7 and front HO2S connector terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and front HO2S.
  3. Measure resistance between ECM connector B136 (30-pin connector) terminal No. 20 and front HO2S connector terminal No. 3. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and front HO2S connector.
  4. Measure resistance between ECM connector B136 (30-pin connector) terminal No. 3 and front HO2S connector terminal No. 2. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring between ECM and front HO2S connector.
  5. Measure resistance between front HO2S terminals No. 2 and No. 4. See Figure. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, replace front HO2S.
  6. Check for poor terminal contact at ECM and front HO2S connectors. Repair connectors as required. If connectors are okay, replace front HO2S. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
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