I have a question about a problem encountered on my car (Audi A3 2004, 2.0TDI automatic sportback).

I noticed my GSG-DSG 0623 gearbox behaving very oddly, like it does not know when to change gears, especially from 3rd gear on.

Putting the tester on it, I've read two codes, P0606 and P0716. P0606 it says that my PCM unit is defective, and the P0716 says that the Input Speed Sensor (G182) is faulty, with the message: Implausible signal.

Now, I'm almost sure the both the PCM and the sensor are working just fine, so I suspect that the gearbox is the main cause (maybe the clutches are slipping), so it sends an out-of-range value to the sensor, which in turn sends an out-of-range value to the PCM, thus causing the error codes.

Does this makes sense to you? How can I test the sensor to make sure it's working correctly? I don't want to just change the components, when the real cause might be somewhere else.

Thank you very much!

  • How many wires on the input speed sensor? is it analog or digital? You'd need a scope to check signal integrity either way. Speed sensors use a trigger wheel to generate a signal so it's unlikely a slipping clutch would set a circuit code. You're going to need wiring diagrams for your car and do some testing. – Ben Feb 26 '17 at 20:54
  • Just an anecdote in reference to the input shaft speed sensor: I had a similar issue on a 99 Jeep WJ (P0716, transmission shifts roughly / won't shift past 2nd), and the sensor was most definitely faulty. I'd suspect it before something in the transmission. – Skies of Solace Feb 27 '17 at 15:44

On some cars, the input speed sensor to the transmission and the output speed sensor work in tandom. The computer can tell which gear the transmission is actually in and even adjust the harshness of the shift. If one sensor has actually failed, typically the car should go into a limp home mode.

Are you sure these are current error codes or simply stored old ones?

If you decide to change the sensor, change them in pairs (input and output) - if one goes, the other one is likely to follow (in my case literally 1 month later)

As for the PCM code - that code simply means that some part of the PCM failed a self check. Could be a bad bit in a memory chip etc. Could also be a weird startup sequence. Pulling battery/replacing battery etc. If the code is not current, don't worry about it. If it is current, replace the PCM. There are plenty of places that will get you a refurbished one at reasonable prices.

I don't think the PCM code is related. I think the sensor code is.

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