P1166

DTC P1166: A/F Sensor (Sensor 1) Heater Circuit Malfunction

1. Reset the ECM/PCM.
2. Start the engine.

Is DTC P1166 indicated?

YES - Go to step 3.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM.




3. Measure voltage between ECM/PCM connector terminals A1 and A24, 30 seconds after the ignition switch is turned ON (II).

Is there battery voltage?

YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.

NO - Go to step 4.




4. Measure voltage between ECM/PCM connector terminals A22 and A24.

Is there battery voltage?

YES - Go to step 5.

NO - Go to step 9.

5. Turn the ignition switch ON
6. Disconnect ECM/PCM connector A (31P).
7. Turn the ignition switch ON (II).




8. Connect ECM/PCM connector terminals E8 to body ground with a jumper wire, then measure voltage between ECM/PCM connector terminals A1 and A24.

Is there battery voltage?

YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.

NO - Repair open or short in the wire between A/F sensor (Sensor 1) and the ECM/PCM (A1).

9. Turn the ignition switch OFF.
10. Disconnect ECM/PCM connector A (31P) and the A/F sensor (sensor 1) 4P connector.




11. Check for continuity between A/F sensor (Sensor 1) 4P connector terminal No.3 and body ground.

Is there continuity?

YES - Repair short in the wire between the A/F sensor relay, the A/F sensor (Sensor 1), and the ECM/PCM (A22).

NO - Go to step 12.

12. Turn the ignition switch ON (II).




13. Measure voltage between ECM/PCM connector terminals E8 and A24.

Is there battery voltage?

YES - Repair open in the wire between the ECM/PCM (A22) and the A/F sensor (Sensor 1) or A/F sensor relay.

NO - Go to step 14.

14. Check the following fuses:
- No.14 OPTION (40A) fuse in under-hood fuse/relay box.
- No.4 ACG (10A) fuse in under-dash fuse/relay box.
- No.2 A/F HEATER (20A) in under-dash fuse/relay box.

Are any of the fuses blown?

YES - Repair short in the wire between the A/F sensor relay and the fuses.

NO - Go to step 15.

15. Check for continuity in the wires between the A/F sensor relay and the fuses.

Is there continuity?

YES - The wires are OK, replace the A/F sensor relay.

NO - Repair open in the wire between the A/F sensor relay and the fuses.