Coolant Temperature

The temperature sensor informs the Integrated Central Electronics (ICE) module of the coolant temperature via pins 5 and 58.

This information is then passed on to the main instrument display panel in the form of a PWM signal when the ignition switch is in the Start or Drive position.

Main instrument display panel 1
Coolant temperature indication in main instrument display panel 1 is controlled by the ICE module, that is to say the temperature indication breakpoints are programmed directly in the ICE module, which sends the information to the main instrument display panel via a non-linear 500 Hz PWM signal. If the temperature falls below -30° C or rises above +160° C (i.e. extends beyond the temperature range limits) for more than 0.5 seconds, the ICE module sets the duty cycle at 5%.

If the temperature is outside the preset limits, the ICE module will assume that the temperature sensor is shorted or that there is no continuity in the circuit. A diagnostic trouble code will then be generated.

Main instrument display panel 2
Coolant temperature indication in main instrument display panel 2 is controlled by the main instrument display panel itself.

The PWM signal from the ICE module has a frequency of 122 Hz and varies linearly between 10% and 90% duty cycle but the main instrument display panel inserts breakpoints at certain temperatures so that the temperature gauge needle will not swing up and down at normal coolant temperatures.