Signal Too High. 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 Ground Lead
- Ignition OFF.
- Wait for approx. 150 seconds (cars with immobilizer 245 seconds).
- Disconnect temperature sensor.
- Connect an ohmmeter between temperature sensor connector terminal 2 (engine control module (ECM) side) and ground.

NOTE: If the engine cooling fan runs on, it must be allowed to stop before taking resistance readings.

- The ohmmeter should read approx. 0 ohms.

If reading is OK:
^ Proceed to: Checking Signal Cable section 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 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: Checking for a Short-circuit section below.





Checking for a Short-circuit
- Check cable between engine coolant temperature (ECT) sensor terminal 1 and engine control module # A31 for a short-circuit to supply voltage.
- Proceed to: Checking Engine Coolant Temperature Sensor section below.





Checking Engine Control Module 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 (DTC) 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.





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 diagram).

If reading is OK:
^ The cause of the diagnostic trouble code has been loose connections in the engine coolant temperature sensor connector.
^ Check connector for contact resistance and oxidation and remedy.
^ Proceed to: Verification section below.

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





Checking Engine Coolant Temperature Sensor
The engine coolant temperature sensor may fail if there has been a short-circuit to voltage supply in 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 diagram).

If reading is OK:
^ Temperature sensor is OK
^ Proceed to: Verification section below.

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





Checking Engine Control Module Connector
- Ignition OFF.
- Temperature sensor disconnected.
- Check engine control module connector for contact resistance and oxidation and remedy.
- Engine control module connected.
- Ignition ON.
- Connect a voltmeter between temperature sensor connector terminals 1 and 2 (engine control module side).
- The voltmeter should read approx. 5 Volts.

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 1 and engine control module # A31 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:
^ Fault not found.