Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Coolant Level
When engine coolant is at the proper level, the low coolant switch is closed. When in this condition, battery voltage is applied to the low coolant circuit 1478 input of the body control module (BCM).
When coolant is below the proper level, the low coolant switch opens. Because no voltage is applied to circuit 1478 the BCM responds by sending a serial data message to the instrument panel cluster to turn ON the low coolant warning light.
The BCM has an internal timer, which will not turn ON the low coolant warning light unless the coolant level is low for greater than 30 seconds. The timer avoids coolant sloshing, falsely turning on the low coolant telltale.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.