Low Coolant Indicator

The "LOW COOLANT" Indicator has system voltage applied in "RUN," "BULB TEST," or "START." The Indicator requires a ground for illumination. There are two ways the Indicator receives a ground:
1. During bulb check through the Instrument Cluster.
2. Whenever the Engine Coolant Level Sensor detects a low coolant condition.

The Instrument Cluster performs a bulb check by grounding the circuit to the indicator for approximately one second after Ignition "ON". When a low coolant condition occurs, a ground path is supplied through the Engine Coolant Level Sensor to the Indicator. At the same time, ground is supplied through the Engine Coolant Level Sensor to the Body Control Module (BCM).The module is designed to provide a continuous ground path to the Indicator for the remainder of the Ignition cycle in which a momentary low coolant condition occurred. (The module provides its own ground to the Indicator until the Ignition is turned off).

With a low coolant level, the circuit made by the low coolant probe has very high resistance (over 50,000 Ohms). The low engine coolant indicator module senses the voltage change at the low coolant level input. The indicator module provides ground to the LOW COOLANT indicator and the indicator lights up. The LOW COOLANT indicator is grounded for 1.5 seconds when the ignition switch is initially turned the ON position, causing the LOW COOLANT indicator to light.