Code 41 Or 42: O2 Sensor Heater
- Turn ignition off. Remove No. 15 (ACG) fuse from underdash fuse box for 10 seconds to reset ECU. Check ECU for fault codes. See RETRIEVING CODES
. If Code 41 or 42 is not present, problem is intermittent. Check connections at ECU connector and O2 sensor connector.
- Test drive vehicle and retest. If Code 41 or 42 is present, turn ignition off. Disconnect 4-pin O2 sensor connector. Measure resistance between O2 sensor terminals "C" and "D". Refer to Fig 1
. If resistance is not 10-40 ohms, replace sensor. If reading is 10-40 ohms, go to next step.
- Check continuity between body ground and all O2 sensor terminals. If continuity is present between any sensor terminal and ground, replace O2 sensor. If continuity is not present between sensor terminals and ground, check for continuity between terminal "A" and terminals "C" and "D". See Fig 1
. If continuity is present, replace O2 sensor. If continuity is not present, go to step 4).
- Turn ignition on. Measure voltage between O2 wiring harness connector Black/Yellow wire and Green/Blue wire (left sensor) or Green/Red wire (right sensor). If battery voltage is present, go to step 7). If battery voltage is not present, measure voltage between Black/Yellow terminal and body ground. If battery voltage is not present, check No. 22 fuse. If fuse is okay, repair open in Black/Yellow wire between O2 sensor and No. 22 fuse. If battery voltage is present, go to step 5).
- Turn ignition off. Connect O2 sensor connector. Connect "A" connector of ECU Test Harness (07LAJ-PT3010A
) to vehicle wiring harness, leaving ECU disconnected. Turn ignition on. Measure voltage between test terminal A10 (+) and test terminal A12 (-) for right O2 sensor or A23 (-) for left O2 sensor. See Figure
.
- If battery voltage is present, substitute a known good ECU, and recheck. If symptom/problem goes away, replace original ECU. Battery voltage is not present, repair open in Green/Blue wire (left sensor) or Green/Red wire (right sensor) between ECU connector and O2 sensor.
- If battery voltage was present in step 4), turn ignition off. Disconnect "A" connector from ECU. Turn ignition on. Measure voltage between O2 wiring harness connector Black/Yellow wire and Green/Blue wire (left sensor) or Green/Red wire (right sensor). If battery voltage is present, repair short in Green/Blue wire or Green/Red wire between ECU connector and O2 sensor.
Courtesy of AMERICAN HONDA MOTOR CO., INC.