Trouble Code Conditions

2-5-1 OUTSIDE TEMPERATURE SENSOR SIGNAL





Condition

- Diagnostic trouble code (DTC) EFI-251 is stored if the engine control module (ECM) receives a signal from the outside temperature sensor corresponding to a temperature below -45°C (-49°F) (signal too high), or higher than +14O°C (284°F) (signal too low).
- Diagnostic trouble code (DTC) EFI-251 is stored if the signal is unstable for 25 seconds (sporadic signal).

Substitute Value
- The engine control module (ECM) adopts an outside temperature of +20°C (68°F).

Possible Source

Signal too High:

- Open-circuit in signal cable or ground lead
- Short-circuit to supply voltage in signal cable
- Contact resistance in terminals
- Defective outside temperature sensor.

Signal too Low:

- Short-circuit to ground in signal cable
- Defective outside temperature sensor.

Signal Sporadic:

- Loose connection
- contact resistance in terminals
- Defective outside temperature sensor.

Fault Symptom(s)

- None.

OTHER DIAGNOSTIC TROUBLE CODES AND STATUS MESSAGES





Other Diagnostic Trouble Codes

- Read off other diagnostic trouble codes (DTCs).
- Are diagnostic trouble codes (DTOs) EFI-123 and EFI-411 stored?

Yes:
- Check common outside temperature sensor and throttle position (TP) sensor terminal #A18 on the engine control module (ECM) for contact resistance, oxidation and for an open-circuit.

No:
- Proceed to test step below.





Status Messages

- Select one of the following options to continue.

Alternative 1:
- Proceed to Signal Too High. Permanent Fault section.

Alternative 2:
- Proceed to Signal Too Low. Permanent Fault section.

Alternative 3:
- Proceed to Signal Sporadic. Permanent Fault section.

Alternative 4:
- Proceed to Signal Too High. Intermittent Fault section.

Alternative 5:
- Proceed to Signal Too Low. Intermittent Fault section.

Alternative 6:
- Proceed to Signal Sporadic. Intermittent Fault section.