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Home >> Subaru >> 1997 >> SVX LSi >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0141 (RO2_H): Rear O2S Heater Circuit Malfunction
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DTC P0141 (RO2_H): Rear O2S Heater Circuit Malfunction

  1. Connect SSM and check for DTC(s). If DTC P0135, P0141 and P0147 do not exist, go to step 3). If DTC P0135, P0141 and P0147 exist, go to next step.
  2. Turn ignition off. Disconnect ECM connector. Check resistance between ECM connector terminal No. 42 and chassis ground. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is 5 ohms or less, repair poor contact in ECM connector. If resistance is more than 5 ohms, repair open in wiring between ECM and coupling connector, open in wiring between coupling connector and engine ground terminal, poor contact in rear O2S connector, poor contact in rear O2S connector or poor contact in coupling connector.
  3. Turn ignition off. Set SSM to function mode F33 to read rear O2S heater current indication. Start and warm engine to normal temperature. If reading is less than 0.2 amp, go to next step. If reading is 0.2 amp or more, repair poor contact in ECM and rear O2S connector.
  4. Start and idle engine. Using DVOM connected to chassis ground, backprobe ECM connector terminal No. 37. If voltage is 1.0 volt or less, go to step 6). If voltage is less than 1.0 volt while wiggling ECM wiring and connector, repair poor contact in ECM connector. If voltage remains 1.0 volt or more, go to next step.
  5. Disconnect rear O2S connector. Backprobe ECM connector terminal No. 37. If voltage is less than 1.0 volt, replace ECM. If voltage is more than 1.0 volt, check for short in wiring between ECM and rear O2S connector. Repair circuit and replace ECM.
  6. Turn ignition off. Disconnect rear O2S connector. Turn ignition on. Check voltage between rear O2S connector terminal No. 2 and chassis ground. If voltage is 10 volts or more, go to next step. If voltage is less than 10 volts, repair poor contact in connector or open circuit in wiring between main relay and rear O2S.
  7. Turn ignition off. Check resistance between rear O2S connector terminals No. 1 and No. 2. If resistance is more than 30 ohms, replace rear O2S. If resistance is 30 ohms or less, repair open in circuit between rear O2S and ECM connector and/or poor contact in rear O2S or ECM connectors.
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