Hi, I'm fitting a towbar to a 2014 Punto. A friend warned me that wiring up the lights could affect the cpu. Hoping that a bypass relay will be all I need to avoid problems.
Anyone had experience / difficulty wiring up a towbar?

Thanks

I had my last towbar with Canbus wiring done professionally. The costs were not silly and they made the connections properly. Some cars have pug in modules.

Well there are three things to consider here:

1) A bypass relay is just a relay switch box with 7 inputs that take next to no current and are connected to the rear lights. These units ensure that the vehicles bulb failure detection does not trigger. These have nothing to do with CAN-Bus even if your vehicle has a CAN-Bus architecture, and certainly will be of no issue or concerrn on a 2014 Punto. These unit require a dedicate 12V power feed capable of supplying 10 to 15 Amps.

2) Some, not all vehicles with CAN-Bus can accept a CAN-Bus trailer control unit. These are Plug & Play boxes. The advantages of using this type of unit is that at a minimum it will disable your reversing sensors (if you have them). These units *may* still require a dedicated 12V power feed to power the trailer lights. This depends on if the vehicle manufacturer has already catered for this trailer lighting power feed. Some do some don't. Suppliers of the units will be able to advise.

3) Multiplexed systems. This is a vague and often confusing term often mixed up with CAN-Bus, etc. I'll use the 500X as an example (to which I have fitted a towbar and all wiring myself). This vehicle is a modern CAN-Bus vehicle. It also accepts a CAN-Bus trailer control unit. However ignore all of that and you will find that the lights are powered by simple 12V feeds for the main part. Where the multiplex comes into play is the rear side lights and brake lights are actually wired in parallel. The different / way these operate is that on side lights the rear lights are feed with 6V not 12V (modulated feed). When the brake is pressed the paralleled lights (side/brake) are fed with the full 12V. Not with this set-up some modern Bypass relays can detect and handle this. If they can't then what happens is this. When you turn the side lights on the trailer side lights come on. When you press the brake pedal the trailer side lights AND brake lights come on. This is perfectly legal and not an issue. For a vehicle following you then on no side lights when you press the brake pedal ALL you rear side lights and brake lights come on. If on side lights then your trailer side lights will be on and then when you press the brake pedal the brake lights will then come on.

I quite like this because when towing in daylight not only do the side and brake lights come on but also the high level corner lights illuminate red as well. If they miss all of that and still run into the back of you then say no more.