Coolant Temperature Signal, Checking

CIS Turbo ECU Harness Connector (Pin # Locations):

CIRCUIT TEST

Test conditions: Engine temperature at least 20~C (68~F).

1. Disconnect harness connector from ECU.

Coolant Temperature Sensor:

2. Using DVM, check resistance between terminal #10 of harness connector and ground.
- Resistance should be approximately that shown in diagram for a given temperature.

If resistance is higher than specified (or infinite), check for:
a. Poor connections or corroded connector terminal at sensor.
b. Open circuit between ECU terminal #10 and sensor.
c. Faulty sensor.

If resistance is lower than specified (or zero), check for:
a. Grounded circuit between ECU terminal #10 and sensor.
b. Faulty sensor.

SENSOR TEST

1. Remove sensor from engine and insert rubber plug to prevent coolant loss.

2. Cool sensor by immersing the temperature sensitive end in ice water (the temp. of ice water is approx. 0~C).

3. When sensor is sufficiently cooled, check resistance between its terminal and the threaded portion of the sensor housing.
- Resistance should be approx. that shown in diagram for 0~C (32~f).

4. Heat sensor by immersing temperature sensitive end in boiling water and recheck resistance (the temp. of boiling water is 100~C/212~F at sea level, slightly less at higher elevations).
- Resistance should be approx. that shown in diagram for 100~C (212~f).

If resistance is not within the specified range for BOTH hot and cold tests, replace sensor.