John/Horace Posted January 25, 2021 Report Share Posted January 25, 2021 The following is pasted from the Ram forums. An electrical engineer circuit designer posted the info which I hadn’t heard before. The original ram thread is also posted below the excerpt from the main discussion, lengthy reading required. Journey uses Can bus, but the led bulb problem is probably not related to that at all it seems. While your statement is technically correct, the context is misleading because of improper terminology used to describe the lighting circuits on Chrysler vehicles. A CAN Bus is a differential bus just like ethernet and requires 120-ohm termination. Google CAN bus for additional. Somewhere along the line, someone labeled Chrysler's lighting circuits as CAN BUS which is completely inaccurate and not true in any way what so ever. The lighting circuits are controlled by an FET (field effect transistor) in the body control module. The FET pulse width modules the circuit to create an effective DC voltage to the lighting source. The FET has the ability to measure the amount of current the lighting circuit is consuming. Based on the threshold values in the calibrations for each lighting circuit, the BCM can determine if the lighting circuit is faulting, for example, short to ground, short to power, open, etc. The issue with the current/late model years is Chrysler has tightened the calibration values for the amount of current that should be flowing on a lighting circuit. If the amount of current is out of range then the BCM can mitigate the circuit often seen as flashing or turning off then back on. In order to trick the lighting circuit FET, it needs to see a load that pulls the same amount of current flow as the halogen bulb which is around 4.3 amps. Solutions are to use a resistor to do this. The ideal solution would be to develop a HID ballast that has a circuit designed to not only consume the 4.3 amps but also power the HID power supply. https://www.ramforumz.com/threads/defeating-canbus-system.224775/ jkeaton 1 Quote Link to comment Share on other sites More sharing options...
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