ZCI 4-Way on 2018 Porsche Cayenne Not Working

Updated 02/03/2026 | Published 07/10/2024

Question:

Hi. I bought your ZCI harness to install on a 2018 Porsche Cayenne. In the installation video it says that the tail light circuit should be installed on a fog light. Can you help me out and identify what wire color/plug number I should “tap to”? Currently I am connected in the following way and the harness does not properly work when headlights are on: Left tail connections: Left turn on pin 4, green with white stripe Tail on pin 3, grey with yellow stripe Stop on pin 2, red with yellow stripe

asked by: Sergei

Expert Reply:

Hello Sergei,

Based on the install of the ZCI Circuit Protected Vehicle Wiring Harness # 119250KIT we did on a 2017 Porsche Cayenne (video linked below) you do have the right wire, the gray wire with the yellow stripe, pin 3, for the taillights. That said, did you test it out? Sometimes wire colors get changed so the only way to know for sure if that's the right wire is test it. Having said that, if the harness is only not working when the headlights are on, the chassis ground isn't good enough. A poor ground results in electrical resistance/bad continuity within the circuits, hence the issues with the lights not working.

expert reply by: Kyle S

Jerred H.

2/3/2026

Hey Sergei, how did things go after checking the ground connection on your Cayenne with the ZCI harness? Did improving the ground fix the issue with the lights when the headlights are on? Your update could make it easier for others troubleshooting the same wiring setup.