I agree with much of this. I did review my posts and catch myself saying "adding resistance", which is technically very not correct. I should have said "adding load", which is done here by adding a resistor. "Adding a resistor" though definitely does not equal "adding resistance" to the circuit so my bad.

Just careful when you intermix "current" with "voltage". LEDs have a forward voltage drop, so the supply voltage must be higher than the drop for current to pass. Powering a single LED with 14.2V is **exactly** what happens! Resistors don't change voltage - they limit current. So it's not the voltage that will kill the bulb if no resistor is present - it's the current.

Edit: I take that back..."adding resistance" IS actually the correct term.

Actually you were closer to correct the first time. The CANBUS LED lamps add a resistor, but because it is wired in parallel to the standard lamp's LED and ballast resistor, it decreases the resistance of the lamp. This increases the current through the lamp, thus increasing the load on the circuit.

You may be powering an LED

__lamp__ with 14.2 V, but that lamp is comprised of (at least) one discrete LED and one resistor, and the LED (or each LED if there is more than one) is only going to see its rated forward voltage and rated current.

Current and voltage are inextricably related in a circuit, especially so for a resistive one. You cannot have current without voltage and, unless it is an open circuit, any time you have voltage you will have a proportional current. You can split hairs about what causes the damage, but since the current that causes the damage is created by the voltage across the LED, it is fair to say that it was too much voltage that caused the failure. Keep in mind that the vehicle's electrical system is a voltage source and not a current source since it is the system's voltage that is regulated.

Also, resistors do change voltage in any circuit that has current flow, because there is a current-induced voltage drop across the resistor. Put two resistors of equal value in series across a 12 V power supply, then measure the voltage at the junction of the two resistors. You will see that it is 6 V, so the resistor has changed the voltage at that point in the circuit.

Assume you are using an LED with a forward voltage of 3 V and a rated current of 250 mA in a 14.2 V circuit. You will need a resistor wired in series with that LED that will cause an 11.2 V drop at 250 mA, so its resistance should be 11.2 divided by 0.250, or 44.8 Ohms. The closest standard value to 44.8 Ohms is 47 Ohms, so that is what would normally be used.