123 Engine Temperature - Above Limit

P0118

123 Engine Temperature - Above Limit

Function
The temperature sensor measures the coolant temperature by means of a variable resistor.
The engine coolant temperature is required for regulating the warm-up phase, for mixture enrichment on start-up, for calculating the ignition angle in the warm-up phase and for controlling the fans. In the event of a fault, a calculated substitute characteristic is used.

Diagnosis conditions

P0115
A temperature model is formed. If the measured temperature deviates too much from the calculated temperature, a fault is detected.

NOTE: A thermostat which is constantly open can cause the fault P0115.

P0117
A fault is recorded after a debounce time of 0.4 seconds if an engine temperature of less than -42 °C is measured.

P0118
A fault is recorded after a debounce time of 0.4 seconds if an engine temperature of more than 140 °C is measured.

P0115 - P0118:

Wiring Diagram







Resistance values
0 °C = 5.0 - 7.0 k ohms
20 °C = 2.0 - 3.0 k ohms
60 °C = 0.4 - 0.8 k ohms

Diagnosis Procedure

Part 1:

Part 2:

1 Check temperature sensor.
1. Remove connector in engine compartment.
2. Connect ohmmeter to temperature sensor connector, pins 1 and 4.

Display: 2 - 3 k ohms at 20 °C.

2 Check output voltage of DME control module.
1. Connect special tool 9637. Do not connect connector III of vehicle wiring harness.
2. Connect voltmeter to pin III/22 (B+) and III/17 (ground).
3. Ignition on.
Display: approx. 5 V

3 Check wiring from DME control module to temperature sensor for continuity.
1. Connect special tool 9637 to wiring harness (DME control module connector).
2. Remove connector of ECT sensor.
3. Connect ohmmeter to special tool 9637, pin III/17, and temperature sensor connector, pin 4.

Display: 0 - 5 ohms

4. Connect ohmmeter to special tool 9637, pin III/22, and temperature sensor connector, pin 1.

Display: 0 - 5 ohms

4 Check wiring from DME control module to temperature sensor for short to ground.
1. Connect special tool 9637 to wiring harness (DME control module connector).
2. Remove connector of ECT sensor.
3. Connect ohmmeter to special tool 9637, pin III/22, and ground.

Display: infinity ohms

If 0 - 5 ohms is displayed, check wiring for chafing and pinching damage.

5 Check wiring from DME control module to temperature sensor for short to B+.
1. Connect special tool 9637.
2. Remove connector of ECT sensor.
3. Connect voltmeter to pin III/22 (B+) and to ground.
4. Switch on the ignition.

Display: approx. 5 V

If battery voltage is displayed, check wiring harness for chafing and pinching damage.

6 Perform adaptation.
1. Switch on the ignition.
2. Wait one minute. Do not press the accelerator.
3. Switch off the ignition for at least 10 seconds.
4. Read out the fault memory.