Honest car modification guides. What every mod does, what improves, what gets worse — so you spend your money right the first time.
Installed LED headlights and now your dashboard is showing a bulb error or check engine light? This is extremely common and almost always fixable in minutes. Here is exactly what causes it and how to solve it.
Your car's electrical system monitors every bulb circuit for resistance. Factory halogen bulbs have a specific resistance — typically 55 watts. LED bulbs draw significantly less current — usually 25-45 watts. When your car's onboard computer detects less current flowing through the headlight circuit than expected it interprets this as a dead or failed bulb and throws a warning light.
This is called a CANBUS error and it is one of the most common issues reported after LED headlight installation. It is not a real problem with your car — it is your car's electronics being too smart for its own good.
This is the correct solution for persistent CANBUS errors. A CANBUS decoder or load resistor plugs in between your car's headlight connector and the LED bulb. It adds resistance to the circuit to simulate the electrical load of a halogen bulb — your car's computer sees the correct resistance and the warning light disappears.
The simplest prevention. CANBUS compatible LED bulbs have the resistance management built into the bulb driver circuit — no external decoder needed. If you have not purchased your LED bulbs yet look for the words CANBUS compatible on the product listing.
Some cars do not throw a warning light but cause the LED bulbs to flicker rapidly. This is caused by the same CANBUS issue — the car's PWM (pulse width modulation) system is incompatible with the LED driver. The solution is identical — CANBUS decoder or CANBUS compatible replacement bulbs.
Quick check: Before buying anything — use an OBD2 scanner to read the fault code. If it specifically says a headlight circuit fault — it is a CANBUS issue and the fixes above apply. If it says something else entirely the LED installation may not be the cause.
Honest car modification guides. What every mod does, what improves, what gets worse — so you spend your money right the first time.