The other day my customer brought in his Mercedes for service. We did the engine service and I have also changed the auto gearbox oil and filter. Something strange happens after the service. The engine started one time while it was still on the stands, I was checking the gears after the gearbox change.
But once the car was on its wheels ready for a test drive, The engine will not run, the starter will start the engine but the engine will not run. It is completely dead. I thought that was strange, I have plugged in the scanner to see if there are any faults. There was only the intake camshaft sensor fault….. I have checked the voltage on the 3 pin plug of the sensor (unplug) with a scope and at no 1 there was 12v, pin no 2 was 0 volt, and pin 3 neg volt. When I plug in the sensor the voltage at Pin 1 dropped to about 4.8v and that was strange to me, What I later found is the fuse that supply voltage to the coils and the cam sensor was blown. This was caused by the tool we use to remove the plugs, the one coil wiring insulation was damaged and it touches the tool when you remove the plug.