DTC EFI-123

1-2-3 ENGINE COOLANT TEMPERATURE SENSOR, SIGNAL





Condition
Diagnostic Trouble Code (DTC) EFI-123 is stored if the Engine Control Module (ECM) receives a signal from the Engine Coolant Temperature (ECT) Sensor corresponding to a temperature lower than -44°C (-47.2°F) (signal high) or higher than +148°C (298.4°F) (signal low). As soon as the engine is started the temperature is calculated theoretically. When the calculated engine coolant temperature (ECT) has reached +75°C (167°F) it is compared with the temperature from the engine coolant temperature (ECT) sensor. Diagnostic trouble code (DTC) EFI-123 is stored if the engine coolant temperature (ECT) sensor signal corresponds to a temperature lower than +58°C (136°F).

Substitute Value

- While the car is being driven the calculated engine coolant temperature (ECT) is adopted.
- When the car is restarted a substitute value of +3O°C (86°F) is adopted and when the engine has started the engine coolant temperature (ECT) is calculated theoretically.
- With ignition on the engine coolant fan operates at low-speed.
- When the engine is running the engine coolant fan operates at high-speed.
- When the engine is switched off the engine coolant fan runs on for a further 3 minutes.
- Idle air trim adaptation disabled.
- Long-term fuel trim disabled.
- Leakage diagnostic is turned OFF.
- Initial boost pressure adopted.

Possible Source(s)

Signal too high:
- Short-circuit to supply voltage in signal cable
- Open-circuit in signal cable or ground lead
- Contact resistance in terminals
- Defective engine coolant temperature (ECT) sensor.

Signal too low:
- Short-circuit to ground in signal cable
- Defective engine coolant temperature (ECT) sensor.

Faulty signal:
- Defective engine coolant temperature (ECT) sensor
- Defective coolant thermostat
- Contact resistance in terminals
- Short-circuit between signal cable and another cable.

Fault symptom(s)
- Difficult to start in certain temperature ranges
- With ignition on the engine coolant fan operates at low-speed
- When the engine is running the engine coolant fan operates at high-speed
- When the engine is switched OFF the engine coolant fan runs on for a further 3 minutes