The PCM determines engine coolant temperature from the coolant temperature sensor. The combination coolant temperature sensor has two elements. One supplies a coolant temperature signal to the PCM, and the other element provides a coolant temperature signal to the instrument panel gauge cluster. As coolant temperature changes, the coolant temperature sensor's resistance changes, resulting in a different input voltage to the PCM and gauge. When the air is cold, the PCM provides a slightly richer air/fuel ratio and higher idle speed until the proper normal operating temperature is reached.
See Figures 1 and 2
- Turn the ignition switch to the OFF position.
- Detach the coolant temperature sensor electrical connector.
- Using a DVOM set to the ohms scale, connect one lead to one terminal of the coolant temperature sensor.
- Connect the other ohmmeter lead to the remaining sensor connector terminal.
- With the engine at normal operating temperature, approximaterly 200°F (93°C), the ohmmeter should read approximately 700-1000 ohms.
- With the engine at room temperature, approximately 70°F (21°C), the ohmmeter should read approximately 7000-13,000 ohms.
- If not within specifications, replace the engine coolant temperature sensor.
REMOVAL & INSTALLATION
See Figures 3, 4 and 5
On the 2.0L SOHC engine, the coolant temperature sensor threads into the rear of the cylinder head. On the 2.0L and 2.4L DOHC engines, the coolant temperature sensor threads into the front of the cylinder head, below the coolant filler neck. On all 2.5L engines, the coolant temperature sensor is located next to the coolant filler neck.