* The BCM itself: The BCM uses transistors and other semiconductor devices to regulate the current to the headlights (or a dedicated DRL circuit) to achieve the DRL function. It doesn't use a single diode in the way some older systems might have.
* Headlight bulbs/modules: On some models, the DRL function might be accomplished by using lower voltage or current to the headlight bulbs themselves.
* Separate DRL modules: Some Suburbans might have dedicated DRL modules that contain various components, including diodes, transistors and resistors for proper current regulation, but this would still not be a single, easily-located diode.
In short, you won't find a single component labeled "DRL Diode." Any troubleshooting of the DRL system would involve checking fuses, wiring, the BCM, and possibly the headlight assembly itself. A professional mechanic with diagnostic tools would be needed for accurate diagnosis and repair.
