EMF PWM interference in a concentric twisted harness

I am planning a concentric wiring harness for my project car. I am pretty sure that I am going to run into a signal interference problem but would like to confirm before I continue planning and order a second Autosport/8STA connector.

My engine has an electric water pump, it mounts directly in place of the factory mechanical water pump. Documentation states that it draws 5 to 10 Amps depending on duty cycle, I will speed control it with a PDM.

It would be nice to run this in the main engine harness, but... Would I be correct in assuming that this would be a bad idea as the pwm of a medium amperage load will interfere with the engines trigger, knock & 0-5v sensor signals?

I do not mind buying another autosport connector to drive the water pump if I have to, as I could use it to power a coolant fan, oil fan etc. Possibly headlights - Or would these flicker slightly with the nearby pulsing current? (Hopefully I am just overthinking it)

If you want to know for sure -- build a test harness and scope all the signals. You are probably overthinking it, but maybe not -- only one way to find out.

Personally, I would not worry about this as i would be running Crank/Cam/Knock sensors within shielded cables within the concentric harness. What is the frequency of the PWM on the coolant pump? The one I use in my car is only running at 50-100 hz.

Alright thanks, I will consider making a test harness, that's a good idea

About 100 - 150hz pump speed, cheers

I've run PWM controlled fans and pumps alongside lights and other wiring with no noticeable effects. I can't say I've scoped it as David suggested.

Good practice to always shield your engine position sensor, wheel speed and knock sensor signals.