Engine Control System

DIAGNOSTIC CHART

Diagnostic Chart:

Diagnosis
Abnormal coolant temperature sensor signal.
Harness connector between ECM and temperature sensor is shorted or open.

Trouble Symptom
Hard to start, poor idling, poor driveability.

CHECK COOLANT TEMPERATURE SENSOR

Resistance Test:

1. Turn ignition OFF.
2. Unplug connector from sensor.
3. Measure resistance between sensor terminals.

Terminals Resistance
No. 1 - 2 2.0 - 3.0 K ohms @ 68°F (20°C)
No. 1 - 2 270 - 370 ohms @ 176°F (80°C)

CHECK HARNESS CONNECTOR BETWEEN ECM AND COOLANT TEMPERATURE SENSOR

Harness Test:

1. Unplug ECM connector.
2. Measure resistance of harness connector between ECM and coolant temperature sensor.

Connector & Terminal Resistance
(E30) 3 - (E4) 1 10 ohms max.
(E30) 11 - (E4) 2 10 ohms max.

Harness Test:

3. Measure resistance of harness connector between coolant temperature sensor and body to ensure no short.

Connector & Terminal Resistance
(E4) 1 - body 10 M ohms min.
(E4) 2 - body 10 M ohms min.