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P0117,P0118

Symptom: CHECK ENGINE lamp on, reluctant to start when engine cold.

P0117 , P0118

Coolant temperature sensor, input to control module low/high, faulty, no continuity or shorting to ground/batt+.


Fault symptom

CHECK ENGINE lamp on, reluctant to start when engine cold.

Condition

The sensor reading is above 140°C (284°F) or below -35°C (-32°F) if the intake air temperature is above -20°C (-4°F).

Note

In the event of a malfunction, the control module adopts a preprogrammed value corresponding to 80°C (176°F), with the result that it may be difficult to start the car when the engine is cold because the fuel-air mixture will be too lean. At ambient temperatures below 10°C (50°F), the outside air temperature will be used for one minute before the control module changes over to the 80°C mode.


Diagnostic procedure


1. Check the operation of the temperature sensor with the ISAT command "COOLANT TEMP" in the "READ FUNCTIONS" menu.

If the temperature sensor is in proper working order, the ISAT should show a temperature of 80-90°C when the engine is hot. If this is the case, proceed with point 6. If it is not, continue as described below.

2. Unplug the temperature sensor connector and check the resistance of the sensor by taking a reading across its pins.



The correct resistance is shown in the table.

C°

F°

Resistance (kilo- ohms)

-10

14

8.3-10.6

20

68

2.3-2.7

40

104

1.0-1.3

60

140

0.56-0.67

80

176

0.29-0.37

90

194

0.20-0.24



If the resistance is not correct, change the temperature sensor.

3. With the temperature sensor connector still unplugged, and with the ignition switch in the Drive position, check the voltage across pins 1 and 2 of the connector.


The voltage should be 5 V. If it is not, continue with the next point.

If the voltage is OK, proceed to point 6.

4. Check the lead between pin 45 of the connector and pin 1 of the sensor's connector for continuity/shorting.


Rectify the wiring if it is defective, or continue as described below.

5. Check whether pin 2 of the sensor's connector is properly connected to sensor ground on pin 30 of the control module.

Rectify the ground lead if it has a fault, or continue with the next point.

6. Clear all trouble codes and drive the car to check whether the trouble code is generated afresh. If it is, turn to for further diagnostic instructions.