Code No. P0117: Engine Coolant Temperature Sensor Circuit Low Input

OPERATION

A power voltage of 5 V is applied to the engine coolant temperature sensor output terminal from the engine-ECU connector terminal WTS.
The power voltage is earthed to the engine-ECU connector terminal WTSE from the engine coolant temperature sensor connector terminal.

FUNCTION

The engine coolant temperature sensor converts the engine coolant temperature into a voltage signal, and inputs the voltage to the engine-ECU.
In response to the signal, the engine-ECU controls the fuel infection amount and the fast idle speed when the engine is cold state.
The engine coolant temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the engine coolant temperature rises. Therefore, the sensor output voltage varies with the engine coolant temperature, and becomes lower as the engine coolant temperature rises.

TROUBLE JUDGEMENT

Check Conditions

Battery positive voltage is 8 - 16 V
2 seconds later after the ignition switch has been in "ON" position or the engine has started up.

Judgement Criterion

The engine coolant temperature sensor output voltage is 0.15 V or less.

FAIL-SAFE AND BACKUP FUNCTION

The engine coolant temperature is controlled to be 80°C (start-up of -25°C)
The EGR control is stopped (fully closed).
The throttle valve is opened (electrical discontinuity).
The DPF regeneration is prohibited.

PROBABLE CAUSES

Failed engine coolant temperature sensor
Short circuit in engine coolant temperature sensor circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

Item 7: Engine coolant temperature sensor

OK:
Engine cold state: At ambient temperature (atmospheric temperature) or equivalent.
Engine hot state: At 80 - 120°C

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).

	Go to Step 2.

STEP 2. Resistance measurement at engine coolant temperature sensor connector (WTS line and WTSE line).

(1)Disconnect the connector, and measure at the sensor side.

(2)Measure the resistance between the engine coolant temperature sensor connector (WTS line) and engine coolant temperature sensor connector (WTSE line).
OK:
Engine coolant temperature at -20°C: 14 - 17 kΩ
Engine coolant temperature at 0°C: 5.1 - 6.5 kΩ
Engine coolant temperature at 20°C: 2.1 - 2.7 kΩ
Engine coolant temperature at 40°C: 0.9 - 1.3 kΩ
Engine coolant temperature at 60°C: 0.48 - 0.68 kΩ
Engine coolant temperature at 80°C: 0.26 - 0.36 kΩ

Q. Is the check result normal?

	Go to Step 3.

	Replace the engine coolant temperature sensor.

STEP 3. Check of short to earth in WTS line between engine-ECU connector and engine coolant temperature sensor connector.

Q. Is the check result normal?

	Go to Step 4.

	Repair the connector(s) or wiring harness.

STEP 4. M.U.T.-III data list

Item 7: Engine coolant temperature sensor

OK:
Engine cold state: At ambient temperature (atmospheric temperature) or equivalent.
Engine hot state: At 80 - 120 °C

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).

	Replace the engine-ECU.