DTC EFI-251

Condition(s)
- 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 +140°C (+284°F) (signal too low) for more than 10 seconds.
- Diagnostic trouble code EFI-251 is stored if the signal is unstable for 25 seconds.

Substitute value(s)
- The engine control module adopts an outside temperature of +20° (+68°F).

Possible source(s)
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 connections.
- Contact resistance in terminals.
- Defective outside temperature sensor.

Fault symptom(s)
- None.





Other Diagnostic Trouble Codes
- Read off other diagnostic trouble codes.
- Are diagnostic trouble codes EFI-123 and EFI-411 stored?

Yes:
^ Proceed to: Checking Components section below.

No:
^ Proceed to: Status Messages section below.





Checking Components
- Check common outside temperature sensor and throttle position (TP) sensor terminal # A18 on the engine control module for contact resistance and oxidation, and for an open-circuit.
- Proceed to: Verification section below.





Verification
After carrying out the repair, check that the fault has been remedied as follows:

- Ignition OFF.
- Reconnect connectors, reinstall components etc.
- Ignition ON.
- Select Volvo Scan Tool (ST) to read off the outside temperature.

NOTE: If the radiator is hot the outside temperature sensor will heat up if the car is stationary.

- Is the outside temperature value within bounds?

Yes:
^ Fault corrected.

No:
^ Fault not found.





Status Messages
Select one of the following options to continue:

Alternative 1:
- Refer to: Signal Too High. Permanent Fault.

Alternative 2:
- Refer to: Signal Too Low. Permanent Fault.

Alternative 3:
- Refer to: Signal Sporadic. Permanent Fault.

Alternative 4:
- Refer to: Signal Too High. Intermittent Fault.

Alternative 5:
- Refer to: Signal Too Low. Intermittent Fault.

Alternative 6:
- Refer to: Signal Sporadic. Intermittent Fault.