After installing aftermarket xenon headlights with LED DRLs, it’s common to encounter issues with the daytime running lights not functioning correctly. While VCDS coding might seem like the solution, it’s crucial to diagnose the problem thoroughly before making any coding changes. This article outlines a practical troubleshooting approach using a real-world example of a user struggling with this exact issue.
Diagnosing the DRL Problem: A Step-by-Step Guide
A forum user reported that their high beams worked fine, but the LED DRLs remained off after installing new xenon headlights. Initial attempts to adjust adaptations in VCDS module 09 proved unsuccessful. This suggests the issue might not be software-related but rather a hardware or installation problem. Let’s delve into the recommended diagnostic process:
Understanding the Wiring: Tracing the DRL Signal
The first step is to understand how the DRL signal travels from the Body Control Module (BCM) to the new headlights. On a typical Rest of World (RoW) MQB platform vehicle, the DRL signal originates from pin #4 on the 10-pin headlight connector.
With aftermarket headlights and a new wiring harness, it’s essential to trace how this pin connects to the 14-pin connector on the new headlight assembly. In OEM setups with non-incandescent headlights, the DRL signal usually terminates at pin #12 on the 14-pin connector.
If the wiring connects pin #4 to pin #12, the setup likely mirrors the OEM configuration. However, if pin #4 connects to a different pin, such as pin #10, the aftermarket headlights might require a separate DC power supply for the DRLs. Consult the headlight manufacturer’s documentation or the seller for clarification.
Voltage Check: Confirming DRL Signal Delivery
After identifying the correct DRL pin on the 14-pin connector, the next step is to confirm the DRL signal’s voltage. With the ignition turned on and the DRLs activated, use a multimeter to measure the voltage at each connection point along the path from the BCM to the LED DRLs.
While the DRL signal utilizes Pulse Width Modulation (PWM), a Dimmwert value of 100 in VCDS should result in a voltage reading near the battery voltage. This confirms that the BCM is sending the correct signal.
Conclusion: Beyond VCDS Xenon Coding
If the voltage readings are correct at the DRL pin on the new headlight assembly but the LEDs still don’t illuminate, the issue likely lies within the headlight unit itself. In such cases, contacting the headlight manufacturer for technical support is recommended.
This troubleshooting process highlights that resolving DRL issues with aftermarket xenon headlights often requires a hands-on approach, focusing on wiring and voltage verification rather than solely relying on Vcds Xenon Coding. Remember to consult the manufacturer’s documentation and seek expert advice when necessary. Thorough diagnostics are key to pinpoint the root cause and ensure a successful fix.
