P0116

DIAGNOSTIC TROUBLE CODES P0116, P0117, PO118
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
Voltage lower than 0.03 V, or
Higher than 4.96 V, or
Abnormal rise in temperature after starting in relation to the programmed model stored in the control module's permanent memory.

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.

Diagnostic Procedure.
1. Check the operation of the temperature sensor with the ISAT command "COOLANT TEMP" in the "OBTAIN READOUTS" 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 step 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.

Resistance Table:

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 step.
If the voltage is OK, proceed to step 6.

4. Check the lead between pin 45 of the MOTRONIC control module 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 step.

6. Clear all trouble codes and drive the car to check whether the trouble code is generated afresh.

If it is, continue at "Before Control Module Replacement" for further diagnostic instructions. Before Replacing A Control Module