LED brake light cause Acadia dead battery, no start condition

LED brake light can cause Acadia dead battery, no start condition

Have you installed an LED brake light, turn signal, or reverse lights in your GM Acadia and now have a dead battery, no start condition? Congratulations, you caused the problem yourself.

GM has determined that LED bulbs may be the cause of a dead battery, inoperative Start/Stop system, and an instrument cluster with backlighting problems.

Many vehicles have a “light out” feature where the modules measure resistance or voltage drop to turn signals, parking and brake lights. Since LED bulbs don’t have a filament, the resistance and voltage drop will be different, tricking the light out system into thinking the bulb is burned out. LED manufacturers offer add on resistors to mimic the resistance and voltage drop of a typical incandescent bulb. If your vehicle uses the resistance or voltage drop method, the resistor may work for you.

But not all car makers use that light out testing routing. In fact, many GM vehicles use a completely different method. If you install LED turn signal, parking and brake lights in an Acadia for example, you may find you’ve created your own Acadia dead battery, no start condition. Here’s why installing LED bulbs don’t work.

The light out system in many GM vehicles work by applying a low voltage signal to the bulb, instead of the typical 12-volt battery voltage normally supplied. Since add on resistors are designed for battery voltage, they’ll return an incorrect reading to the body control module (BCM).

BCM stays awake if you use LED bulbs

Since the BCM receives an incorrect return value, it will continue to monitor the circuit which prevents the BCM from going into sleep mode which drains the battery. The discharged battery causes a no start condition, irregular instrument cluster lighting and an inoperative start/stop function.

Fix Acadia dead battery, no start condition

If you’ve replaced any bulbs with LED replacements, remove them and reinstall incandescent bulbs. Then charge the battery. If the problem goes away, the LED bulbs were the cause.

No good reason to use LED brake light bulbs, LED turn signal bulbs, or LED parking bulbs

In general it’s a bad idea to retrofit LED bulbs in place of incandescent bulbs, even if you use resistors. First, it’s not cost effective. You will never recoup the cost of an LED replacement bulb when compared to the cost of incandescent bulbs. Second, in many cases, replacing an incandescent bulb with an LED unit can actually cause major electrical problems as shown above. Third, unless you’re buying LED brake light, turn signal or reverse light bulbs from a reputable supplier, chances are they won’t last anywhere near the published life. It’s not the circuit-on-board (COB) that fails, it’s the LED driver. Quality LED drivers cost more than run of the mill drivers from China. BEWARE of cheap replacements.

©, 2019 Rick Muscoplat