i feel ya pain, very hard to run cables and get easy access, i had trouble 2 probs, at the same time ,one gps not working turned out to be cpu, that was np, but also at the same time had a rear senser that didnt work tested in parking mode not working, tested same sensor with the alp tester and it works, also re set default for # of sensers only shows three connected yet all four work when using tester, aint got a gun for proper testing, but been hit front and rear np got me flustrated, the whole system is now out of the car waiting for new one to come, so apart from ohm's meter is there any other checks or do i install all new gear to go with the recent new cpu the system is bout 4 years old the heads are P2 , are the new connecters better that the old din and better water proof