Faulty Signal. Permanent Fault.

Checking Engine Coolant Temperature Sensor Signal

WARNING: Before fault-tracing disconnect engine cooling fan (FC) relay connector A so that the engine cooling fan will not run. Diagnostic trouble code (DTC) EFI-514 Engine cooling fan low-speed, signal may be stored. After fault-tracing reconnect connector.

- Connect a multimeter 999 6525 with temperature box 999 5281 and temperature sensor 999 5282.
- Carefully remove the expansion tank cap.

WARNING: THE COOLANT MAY BE 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 list.
- Start engine and run up to working temperature. The engine should be warm enough for the thermostat to open.
- Check that the engine coolant temperature (ECT) is within bounds.
- Is the temperature within bounds?

Yes:
^ Try a new coolant thermostat.
^ Then proceed to Verification section below.

No:
^ Proceed to test step below.





Checking The Engine Coolant Temperature Sensor
- Ignition on.
- Go into scrolling value list,
- Disconnect engine coolant temperature sensor.
- Read 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 test step below.





Checking The Engine Control Module Connector
- Ignition off.
- Engine coolant 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 value list.
- Read voltage across engine coolant temperature sensor.
- The reading should be approx. 5 Volts.

If reading is OK:
^ The diagnostic trouble code was caused by poor contact in the engine control module connector.
^ Then 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.
^ Then proceed to Verification section below.





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

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

If reading is incorrect:
^ Proceed to test step below.





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

If reading is OK:
^ The diagnostic trouble code was caused by poor contact in the engine control module connector.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Check cable between the engine coolant temperature sensor terminal 2 and engine control module # A18 for an open-circuit.
^ Then 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 a multimeter 999 6525 with temperature box 999 5281 and temperature sensor 999 5282
- Carefully remove the expansion tank cap.

WARNING: THE COOLANT MAY BE 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 up to working temperature. The engine should be warm enough for the thermostat to open.
- Go into scrolling value list.
- Read engine coolant temperature.
- Is the engine coolant temperature value within bounds.

If reading is OK:
^ Fault corrected.

If reading is incorrect:
^ Proceed to test step below.

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

- Do you want to exit fault-tracing?

Yes:
^ Fault not corrected.

No:
^ Return to Checking Engine Coolant Temperature Sensor Signal section above.