Code 41 Or 42: Ho2S Heater
- Turn ignition off. Remove ACG fuse (No. 15, 7.5-amp) from underdash fuse box for 10 seconds to reset ECM. Check ECM for fault codes. If Code 41 or 42 is not present, problem is intermittent. Check connections at ECM, HO2S and wiring harness connectors. Test drive vehicle and retest.
- If Code 41 or 42 is present, turn ignition off. Disconnect 4-pin HO2S connector. Measure resistance between HO2S terminals "C" and "D". See Fig 1
. If resistance is not 10-40 ohms, replace sensor. If resistance is 10-40 ohms, go to next step.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- Check continuity between body ground and all HO2S terminals. If continuity is present between any sensor terminal and ground, replace HO2S. 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 HO2S.
- If continuity is not present, turn ignition on. Measure voltage between HO2S 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 present, go to step 5. If battery voltage is not present, check FUEL PUMP fuse (No. 22, 20-amp). If fuse is okay, repair open in Black/Yellow wire between HO2S and FUEL PUMP fuse.
- Turn ignition off. Connect HO2S connector. Connect connector "A" of ECM Test Harness (07LAJ-PT3010A
) to vehicle wiring harness, leaving ECM disconnected. Turn ignition on. Measure voltage between test terminal A23 (-) and test terminal A10 (+) for left HO2S or test terminal A12 (+) for right HO2S. See Figure
.
- If battery voltage exists, replace ECM and retest. If battery voltage is not present, repair open in Green/Blue wire (left sensor) or Green/Red wire (right sensor) between ECM connector and HO2S.
- If battery voltage was present in step 4, turn ignition off. Disconnect connector "A" from ECM. Turn ignition on. Measure voltage between HO2S 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 or Green/Red wire between ECM connector and HO2S. If battery voltage exists, replace ECM and retest.