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Parking light fuse blows, Chevrolet

What causes parking light fuse to blow?

Parking light fuse blows Chevrolet

Shops report a slew of parking light fuse issues on some Chevrolet Malibu vehicles. The parking light circuit is controlled by the headlight switch built into the multifunction switch, parking light relay and the body control module (BCM). The problem arises when the parking light fuse blows and you replace the fuse. As soon as you turn on the parking lights or headlights, the parking light fuse blows again. This can lead you to think there’s a short to ground in either the parking light relay or the BCM. Either are possible. But there’s a third option.

Parking light circuit

In a vehicle with a BCM, the multifunction switch doesn’t actually switch power to the parking lights. Instead, the multifunction switch acts as a signal input to the BCM. The BCM provides ground to the control coil circuit of the parking light relay. Once the relay control coil receives ground from the BCM, the contacts close, providing power to the parking lights AND the BCM. Here’s where the third possibility comes into play. If the relay provides power to the parking lights, why does it also have to provide the same power to the BCM? Simple, so the BCM can provide power to the instrument cluster and the heater control to provide illumination at night. The indicator light in the instrument cluster alerts the driver that the headlight parking lights are on and the heater control illuminates so the driver can see the setting on the heater control.

parking light fuse

Parking light fuse and circuit

But what causes the parking light fuse to blow?

It makes no sense, but GM didn’t provide separate fusing for the instrument cluster or the heater control lights. If there’s a short to ground on the grey wire from the BCM to either the instrument cluster or the heater control, it will blow the parking light fuse! That will cause you to waste a lot of time and money replacing the relay and BCM when those aren’t the problem. Instead, isolate the grey wire in connector C2 at the BCM and find the short to ground. That will fix the parking light fuse blows problem.

©, 2018 Rick Muscoplat

 

Posted on by Rick Muscoplat

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