I've got a '05 VW Caddy 2.0 SDI here that didn't run at first. Scanning the OBD (with a chinese knock-off ELM327 scanner, and the Torque Pro App) gave me a P0726 fault code. The description says "Engine Speed Input Circuit Range/Performance". My bet was that the crankshaft sensor was at fault, so I ordered a new one and installed it. The Caddy runs again now, but it won't ever rev past 3500 rpm. Not at standstill or while driving with a warmed up engine. I erased the error, but it reappeared again after a while.
Next to the rev limit thing, it starts terribly bad; it takes a second or 6. The glow plugs light is blinking, but it's still hard to start when the engine is warm, so I guess it isn't caused by the glow plugs.
The car does not hesitate under acceleration, it doesn't smoke, nothing is out of the ordinary. It is a manual, by the way. Could it be that there's something else wrong, or that my chinese scanner misses/doesn't recognise a fault code?