Question Car audio

Feb 20, 2021
Recently I changed my car and reinstalled my kenwood dab/bluetooth head unit in my new car which is a saab. I had to purchase a connects2 wiring harness so that I could use the steering wheel controls on the saab. Everything worked fine. Then I decided to wire in my sub box, this was also in my last car and worked brilliantly.
After wiring the amp in I couldn't get hardly any sound out of the sub, it's working but barely. So I purchased a new wireing kit and re wired the sub amp completely thinking maybe there was a break somewhere. All new wires, rca cables and I checked all the power and earth thoroughly with a multi metre and sll is good but the problem persists. I can't help but think it must be to do with the connects2 wiring harness as it's the only thing that is different on the set up. Any adv