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Code 41 - O2 Sensor Heater 2.1L

  1. Turn ignition off. Remove appropriate fuse for 10 seconds to reset ECU. See CLEARING CODES  . Start engine. Verify if CHECK ENGINE light is on and if LED is flashing Code 41. If Code 41 is present, go to next step. If Code 41 is not present, problem is intermittent. Check connections at O2 sensor, related circuits and at ECU.
  2. Turn ignition off. Disconnect 4-wire connector from O2 sensor. Measure resistance between connector terminals "A" and "B" on O2 sensor. See Fig 1 . If resistance is 15-20 ohms, go to next step. If resistance is not 15-20 ohms, replace O2 sensor.
  3. Check for continuity from each terminal of O2 sensor to ground. If continuity exists, replace O2 sensor. If continuity does not exist, check for continuity between O2 sensor terminal "A" and terminals "C" and "D" individually. See Fig 1 . If continuity does not exist, go to next step. If continuity exists, replace O2 sensor.
    Fig 1: Heated O2 Sensor Connector Terminal ID (2.1L)
    G90G14809Courtesy of AMERICAN HONDA MOTOR CO., INC.
  4. Measure voltage between positive Yellow/Black terminal and negative Black terminal. If battery voltage does not exist, go to step 6). If battery voltage exists, disconnect connector "A" at ECU. Measure voltage between positive Yellow/Black terminal and negative Black terminal.
  5. If there is now battery voltage, repair short in Black wire between ECU terminal A6 and O2 sensor. If battery voltage does not exist, substitute a known good ECU. If condition is corrected, replace original ECU.
  6. Measure voltage between Yellow/Black terminal and ground. If battery voltage does not exist, repair open in Yellow/Black wire between O2 sensor and main relay. If battery voltage exists, turn ignition off. Reconnect 4-wire connector to O2 sensor.
  7. Connect ECU Test Harness connector "A" to main harness, not ECU. Turn ignition on. Measure voltage between terminal A6 (+) and A23 (-). If battery voltage does not exist, repair open in Orange/Black wire between ECU terminal A6 and O2 sensor. If battery voltage exists, substitute a known good ECU. If condition is corrected, replace original ECU.
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