Faulty Signal. 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 Engine Coolant Temperature Sensor Signal
- 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.
- Go into scrolling values.
- Start engine and run up to operating temperature. The engine should be hot enough for the thermostat to open.
- Check that the engine coolant temperature (ECT) is within its permitted range.
- Is the temperature within its permitted range?

Yes:
^ Proceed to: Faulty Signal section below.

No:
^ Proceed to: Checking Engine Coolant Temperature Sensor section below.

Faulty Signal
- This diagnostic trouble code (DTC) can be stored if the thermostat is faulty or if the tolerance of the engine coolant temperature sensor is incorrect within its measurement range.
- Read off frozen values. If the frozen value for engine coolant temperature is outside its permitted range (lower than outside temperature when the diagnostic trouble code is stored for example) then the engine coolant temperature sensor is faulty. Check that the thermostat opens at the correct temperature.
- Replace both components if no faults are detected in either.
- Proceed to: Verification section below.





Checking Engine Coolant Temperature Sensor
- Ignition ON.
- Go into scrolling values list.
- Disconnect temperature sensor.
- Read off voltage across engine coolant temperature sensor.
- The reading should be approx. 5 Volts.

If reading is OK:
^ Proceed to: Checking Ground Lead section below.

If reading is incorrect:
^ Proceed to: Checking ECM Connector section below.





Checking ECM Connector
- Ignition OFF.
- Temperature sensor disconnected.
- Check engine control module (ECM) connector for contact resistance and oxidation and remedy.
- Engine control module connected.
- Ignition ON.
- Go into scrolling values list.
- Read off voltage across engine coolant temperature sensor.
- The reading should be approx. 5 Volts.

If reading is OK:
^ The cause of the diagnostic trouble code (DTC) has been loose connections in the engine control module connector.
^ Proceed to: Verification section below.

If reading is incorrect:
^ Check cable between engine coolant temperature sensor terminal 1 and engine control module # A31 for a short-circuit to another cable.
^ Proceed to: Verification section below.





Checking Ground Lead
- Ignition OFF.
- Wait for approx. 150 seconds (cars with immobilizer 245 seconds).
- Temperature sensor disconnected.
- Connect an ohmmeter between temperature sensor connector terminal 2 (engine control module side) and ground.
- The ohmmeter should read approx. 0 ohms.

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

If reading is incorrect:
^ Proceed to: Checking ECM Connector section below.





Checking ECM Connector
- Ignition OFF.
- Temperature sensor disconnected.
- Check engine control module connector for contact resistance and oxidation and remedy.
- Engine control module connected.
- Connect an ohmmeter between temperature sensor connector terminal 2 (engine control module side) and ground.
- The ohmmeter should read approx. 0 ohms.

If reading is OK:
^ The cause of the diagnostic trouble code has been loose connections in the engine control module connector.
^ Proceed to: Verification section below.

If reading is incorrect:
^ Check cable between temperature sensor terminal 2 and engine control module # A18 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.
- Connect engine cooling 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:
^ Proceed to: Fault-tracing Information section below.

Fault-tracing Information
The verification result shows that the fault persists.

- Do you want to exit fault-tracing?

Yes:
^ Fault not corrected.

No:
^ Fault not found.