Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information EFI-123

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 (signal high) or higher than 148°C (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 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.

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 30°C 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 3 minutes.
- idle air trim adaptation disabled
- long-term fuel trim disabled
- leakage diagnostic is disabled.
- initial boost pressure adopted.

Possible source

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 3 minutes.