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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?

Bart
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2 Answers2

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P0726 fault code can be caused by:

  • A failed engine input speed sensor
  • A failed transmission output speed sensor
  • A short or open in the wiring harness to one of the sensors
  • A loose connection to one of the sensors
  • A faulty crankshaft position sensor
  • A faulty shift solenoid
  • Dirty, contaminated or low transmission fluid
Carguy
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To diagnose the problem easily, you have to use a tool like VCDS to read VAG specific values and error codes which are much more detailed. The common ELM327 readers will only read the OBD values which are rather limited and generic. VAG tools can read the actual problem codes. You can also read codes from other components which OBD scanners can not read. There are other tools than VCDS which can read VAG codes. Fortunately you can buy chinese cables less than $20 still.

Your car (2K) uses CAN-bus so you can't use VCDS lite.

For example: http://www.ross-tech.com/vag-com/tour/dtc_screen.html The OBD code is P1282 in the example, but the VAG tool can read the actual status of the engine when the error was logged, and also the sensor which gave faulty reading and also possible reason of the sensor malfunction.

Here is VW caddy specific info page which shows the actions you can perform: http://wiki.ross-tech.com/wiki/index.php/VW_Caddy_(2K)

Evren Yurtesen
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