Faulty Signal. Permanent Fault.

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 (FC) will not run. Diagnostic Trouble Code (DTC) EFI-514 engine cooling fan (FC) low-speed, signal may be stored. After fault-tracing the connector must be reconnected.

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

WARNING! The water may be extremely 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 to normal operating temperature.
- The engine should be hot 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 Engine Coolant Temperature Sensor

- Ignition ON.
- Go into scrolling value list.
- Disconnect temperature sensor.
- Read voltage across engine coolant temperature (ECT) 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 Engine Control Module Connector

- Ignition OFF.
- Temperature sensor disconnected.
- Check engine control module (ECM) connector for contact resistance and oxidation and remedy.
- Engine control module (ECM) connected.
- Ignition ON.
- Go into scrolling value list.
- Read voltage across engine coolant temperature (ECT) sensor.

The reading should be approx. 5 Volts.

If reading is OK:
- The diagnostic trouble code (DTC) has been caused by loose connections in the engine control module (ECM) connector.
- Then proceed to Verification section below.

If reading is incorrect:
- Check cable between engine coolant temperature (ECT) sensor terminal 1 and engine control module (ECM) #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).
- Temperature sensor disconnected.
- Connect an ohmmeter between temperature sensor connector terminal 2 (engine control module (ECM) side) and ground.

The ohmmeter should read approx. 0 Ohms.

If reading is OK:
- Try a new engine coolant temperature (ECT) sensor.
- Then proceed to Verification section below.

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





Checking Engine Control Module Connector

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

The ohmmeter should read approx. 0 Ohms.

If reading is OK:
- The diagnostic trouble code (DTC) has been caused by loose connections in the engine control module (ECM) connector.
- Then proceed to Verification section below.

If reading is incorrect:
- Check cable between the temperature sensor terminal 2 and engine control module (ECM) #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 999 528 land 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 (ECT).

Is the engine coolant temperature (ECT) 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.