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Code 41: Ho2S Heater

  1. Turn ignition off. Remove BACK-UP fuse (10-amp) from underhood fuse/relay box for 10 seconds to reset ECM. Check ECM for fault codes. If Code 41 is not present, problem is intermittent. Check for poor connections at ECM connector and HO2S. Test drive vehicle and retest.
  2. If Code 41 is present, turn ignition off. Remove HO2S covers. Disconnect 4-pin HO2S connector. Measure resistance between HO2S terminals "C" and "D". See Figure . If resistance is not 10-40 ohms, replace sensor. If resistance is 10-40 ohms, go to step 3).
  3. Check continuity between body ground and HO2S terminals "C" and "D". If continuity is present, replace sensor. If continuity is not present, check for continuity between terminal "D" and terminals "A" and "B". See Figure . If continuity is present, replace sensor. If continuity is not present, go to step 4).
  4. Turn ignition on. Measure voltage between Yellow/Black (+) and Pink/White (-) wire terminals at HO2S wiring harness connector. If battery voltage is not present, go to step 7). If battery voltage is present, disconnect connector "A" from ECM. Measure voltage between Yellow/Black and Pink/White wire terminals at HO2S wiring harness connector.
  5. If battery voltage is present, repair short circuit in Pink/White wire between ECM connector terminal A6 and HO2S. If battery voltage is not present, turn ignition off. Reconnect HO2S. Connect connector "A" of ECM Test Harness (07LAJ-PT3010A ) to vehicle wiring harness, leaving ECM disconnected.
  6. Connect ammeter between test terminals A6 (+) and A23 (-). Turn ignition on. Monitor ammeter for 5 minutes. If current is less than 0.1 amp, replace HO2S. If current is not less than 0.1 amp, replace ECM and retest.
  7. If battery voltage was not present in step 4), measure voltage between Yellow/Black wire terminal at HO2S wiring harness connector and body ground. If battery voltage is not present, repair open in Yellow/Black wire between HO2S and main relay. If battery voltage is present, turn ignition off. Reconnect HO2S wiring harness connector.
  8. Connect connector "A" of ECM Test Harness (07LAJ-PT3010A ) to ECM wiring harness, leaving ECM disconnected. Turn ignition on. Measure voltage between test terminals A6 (+) and A23 (-). If battery voltage is not present, repair open in Pink/White wire between ECM connector terminal A6 and HO2S. If battery voltage is present, replace ECM and retest.
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