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 wires at C102 (located under the under-hood fuse/relay box), A/F Sensor relay, the A/F Sensor (Sensor 1) and the ECM/PCM.

3. Check the following fuses:

- POWER SEAT (20 A) fuse in the under-hood fuse/relay box.
- No.4 ECU (ECM/PCM) CRUISE CONTROL (15 A) fuse in the driver's under-dash fuse/relay box.
- No.6 LAF HEATER (20 A) in the passenger's 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 4.




4. Measure voltage between ECM/PCM connector terminals B19 and B20, 30 seconds after the ignition switch is turned ON (II).

Is there battery voltage?

YES - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM.

NO - Go to step 5.




5. Measure voltage between ECM/PCM connector terminals C13 and B20.

Is there battery voltage?

YES - Go to step 6.

NO - Go to step 10.

6. Turn the ignition switch OFF.
7. Disconnect ECM/PCM connector B (25P).
8. Turn the ignition switch ON (II).




9. Connect ECM/PCM connector terminal B16 to body ground with a jumper wire, then measure voltage between ECM/PCM connector terminals B19 and B20.

Is there battery voltage?

YES - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM.

NO - Repair open or short in the wire between A/F Sensor (Sensor 1) and ECM/PCM (B19).

10. Turn the ignition switch OFF.
11. Disconnect ECM/PCM connector B (25P) and the A/F Sensor (Sensor 1) 4P connector.




12. 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 (Sensor 1) and ECM/PCM (B19).

NO - Go to step 13.

13. Turn the ignition switch ON (II).




14. Measure voltage between ECM/PCM connector terminals B16 and B20

Is there battery voltage?

YES - Repair open in the wire between the ECM/PCM (C13) and the A/F Sensor (Sensor 1) or Secondary HO(2)S (Sensor 2).

NO - Go to step 15.

15. Check for continuity in the wires between A/F Sensor 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.