Diagnostic Detection Logic

DIAGNOSTIC DETECTION LOGIC
Background Information
- The engine coolant temperature sensor converts the engine coolant temperature to a voltage and outputs it.
- The engine control module checks whether the voltage is within a specified range. In addition, it checks the engine coolant temperature (signal) does not drop while the engine is warming up.

When a Fault May Be Recorded
- Ignition switch : ON for more than 60 seconds
- More than 60 seconds after the the engine is started.
- Engine speed is approx. 50 r/min. or more.

What Abnormality Sets This Code
- Sensor output voltage is 4.6 V or more (corresponding to an engine coolant temperature of -45°C (49°F) or less for 4 seconds.
OR
- Sensor output voltage is 0.1 V or less (corresponding to an engine coolant temperature of 140°C (284°F) or more for 4 seconds.
OR
- The sensor output voltage increases from 1.6 V or less (corresponding to an engine coolant temperature of 40°C (104°F) or more) to 1.6 V or more (corresponding to an engine coolant temperature of 40°C (104°F) or less).

- After this, the sensor output voltage is 1.6 V or more for 5 minutes.

Effect on the Vehicle Systems
Vehicle enters Limp-in mode
- Engine Control Module controls as if the engine coolant temperature is 80°C (176°F).

Probable Causes
- Engine coolant temperature sensor failed.
- Open or shorted the engine coolant temperature sensor circuit, or loose connector.
- Engine control module failed.

TROUBLESHOOTING HINTS
If, during engine warm-up, the fast-idling speed is not correct, or black smoke is emitted, the problem is usually a malfunction of the coolant temperature sensor.