DTC 41: Primary HO2S (Sensor 1) Heater Circuit Malfunction Reset the ECM/PCM (see page 11-468). Start the engine. Is the MIL on and does it indicate DTC 41? YES - Go to step 3. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the primary HO2S (Sensor 1) and at the ECM/PCM. Turn the ignition switch OFF. Disconnect the primary HO2S (Sensor 1) 4P connector. At the primary HO2S side, measure resistance between the primary HO2S 4P connector terminals No. 3 and No. 4. PRIMARY HO2S (SENSOR 1) 4P CONNECTOR Wire side of female terminals Is there 10-40 ohms? YES - Go to step 6. NO - Replace the primary HO2S (Sensor 1).

Check for continuity between body ground and the primary HO2S 4P connector terminals No. 3 and No. 4 individually. PRIMARY HO2S (SENSOR 1) 4P CONNECTOR Wire side of female terminals Is there continuity? YES - Replace the primary HO2S (Sensor 1). NO - Go to step 7. Turn the ignition switch ON (II). Measure voltage between the primary HO2S (Sensor 1) 4P connector terminal No. 3 and No. 4. PRIMARY HO2S (SENSOR 1) 4P CONNECTOR Terminal side of male terminals Is there battery voltage? YES - Go to step 9. NO - Go to step 12. Turn the ignition switch OFF. Disconnect ECM/PCM connector A (31P).