Signal Too Low. Permanent Fault

WARNING: Before fault-tracing, disconnect engine cooling fan (FC) relay connector A so that the engine cooling fan will not run. The diagnostic trouble code (DTC) EFI-514 Engine cooling fan lowspeed, signal may be stored. After fault-tracing the connector must be reconnected.





Checking Signal Cable
- Ignition ON.
- Go into scrolling values.
- Disconnect temperature sensor.
- Read off voltage across engine coolant temperature (ECT) sensor.
- The Volvo Scan Tool (ST) should read approx. 5 Volts.

If reading is OK:
^ Try a new engine coolant temperature sensor.
^ Proceed to: Verification section below.

If reading is incorrect:
^ Check cable between temperature sensor terminal 1 and engine control module (ECM) # A31 for a short-circuit to ground.
^ 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.
- Connect engine ccoling fan.
- Connect multimeter 999 6525 with temperature box 999 5281 and temperature sensor 999 5282.
- Carefully remove the expansion tank cover.

WARNING: Coolant is hot.

- Clamp the hose between the radiator and thermostat housing using a hose clip and disconnect the hose from the thermostat housing.
- Insert sensor in thermostat housing and reinstall hose.
- Remove hose clip.
- Start engine and run to normal operating temperature. The engine should be hot enough for the thermostat to open.
- Go into scrolling values.
- Read off engine coolant temperature.
- Is the engine coolant temperature value within its permitted range.

If reading is OK:
^ Fault corrected.

If reading is incorrect:
^ Fault not found.