Signal Too High. Permanent Fault

SIGNAL TOO HIGH. PERMANENT FAULT





Checking Ground Lead

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.

- Ignition OFF.
- Wait for about 150 seconds.
- Disconnect temperature sensor.
- Connect an ohmmeter between temperature sensor connector terminal 2 (Engine Control Module side) and ground.

NOTE! If the engine cooling fan continues operating after engine has been switched OFF, it must be allowed to STOP before resistance measurements are taken.

The ohmmeter should read approx. 0 Ohms.

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

If reading is incorrect:
- Proceed to Checking Engine Control Module Connector section below.





Checking Signal Cable

- Ignition on.
- Temperature sensor disconnected. Connect a voltmeter between temperature sensor connector terminals 1 and 2 (engine control module (ECM) side).

The voltmeter should read approx. 5 Volts.

If reading is OK:
- Proceed to Checking Temperature Sensor Resistance section below.

If value is Lower:
- Proceed to Checking Engine Control Module Connector section below.


If value is Higher:
- Proceed to test step below.





Checking for a Short-Circuit
- Check cable between the engine coolant temperature (ECT) sensor terminal 1 and engine control module #A31 for a short-circuit to supply voltage.

Then proceed to Checking Engine Coolant Temperature Sensor section 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.
- 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.
- Proceed to Verification section below.





Checking Temperature Sensor Resistance

- Ignition OFF.
- Temperature sensor disconnected.
- Connect an ohmmeter between temperature sensor connector terminals 1 and 2 (temperature sensor side).





The ohmmeter should read approx. 2,200 Ohms at +25°C (77°F) (see image).

If reading is OK:
- The cause of the diagnostic trouble code (DTC) has been loose connections in the engine coolant temperature (ECT) sensor connector.
- Check connector for contact resistance and oxidation and remedy.
- Then proceed to Verification section below.

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





Checking Engine Coolant Temperature Sensor:

Hint: The engine coolant temperature (ECT) sensor may malfunction if there is short-circuit to voltage supply of the signal cable. Check the temperature sensor as follows:

- Ignition OFF.
- Temperature sensor disconnected.
- Connect an ohmmeter between temperature sensor connector terminals 1 and 2 (temperature sensor side).





The ohmmeter should read approx. 2,200 Ohms at +25°C (77°F) (see image).

If reading is OK:
- Temperature sensor is OK.
- Then proceed to Verification section below.

If reading is incorrect:
- Try a new engine coolant temperature (ECT) sensor.
- Then proceed to Verification section 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.
- Connect a voltmeter between temperature sensor connector terminals 1 and 2 (engine control module (ECM) side).

The voltmeter should read 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 the engine coolant temperature (ECT) sensor terminal 1 and engine control module (ECM) #A31 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 VERY 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 Ground Lead section above.