Do wiring harnesses need to be replaced? electrical system Nov 17, 2015Q: Do wiring harnesses need to be replaced? As automotive electrical systems increase with each model year, so does the amount of wiring required to operate them. BMW says their current models can contain up to a mile of wires..P0406 OBD-II Trouble Code: Exhaust Gas RecirculationFeb 07, 2019P0325 OBD-II Trouble Code: Knock Sensor MalfunctionFeb 07, 2019How Long Do Wiring Harnesses Last? | YourMechanic Advice How to Replace a Crankshaft Position Sensor - YourMechanic See more results You know you've got a bad engine wiring harness if May 20, 2009What happened: Following an engine change-out, the embrittled wiring harness between the sensors and PCM began touching randomly. The PCM though the engine wasn't idling fast enough, so told the engine to rev faster than it needed to. The engine idled at about 5000 RPM when the clutch was depressed, which made shifting interesting.