P0725-Engine Speed Sensor Malfunction

Had my emissions done yesterday (full out, 40, 50, 60 mph on dyno, 10 sec each). Car passed (barely) but when I went to start it after work, it cranked for a few seconds, but no start. I turned the key off, tried again and it started right up. CEL came on with a P0725. Cleared it and so far so good.

Anybody run into this?

Speed Signal, Checking IIRC if the Speed Signal sensor dies the car will not start. Never happened to me but here is what my Bentley Factory Service manual says to do:

Speed Signal, Checking

• The following procedure requires a test drive. Observe all safety precautions. Refer t

• Special tools, testers and auxiliary items required

• Multimeter .

• Wiring diagram.

• Test requirements

• The Speedometer G21 OK.

• The Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) J248 fuses OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

• Function test

• Connect the scan tool.

• Perform a road test with a vehicle speed greater than 5 Km/h.

• Using the scan tool, Check the vehicle speed:

Diagnostic text Specified value Vehicle Speed Approx. Vehicle Speed

• Compare the vehicle speed on the scan tool to the Speedometer G21 .

• Specified value: a difference of no greater than 10%

• If the specified value was not obtained or no speed was displayed:

• Check the wiring from the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) J248 electrical harness connector T121/16 to the Instrument Cluster Control Module J285 for an open circuit, Short to Battery (+), or to Ground (GND).

• Check the wiring connection for damage, corrosion, loose or broken terminals.

• If necessary, repair the faulty wiring connection.

• Final procedures

• After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to .
2. If necessary, erase the DTC memory. Refer to .
3. If the DTC memory was erased, generate readiness code. Refer to .

• End of diagnosis

• Copyright © 2006 Volkswagen of America, Inc. and Bentley Publishers. All rights reserved. Last processed:

OK. I was really just wondering if the dyno test could have caused this. I drove 2 miles after the emissions to work and it sat for 8 hours. Did not start on the first crank (5 sec). Did on the second, but threw the CEL. Cleared it. Started it up again and it hasn't returned.

Last year, it thre an "excessive clutch slippage" CEL after the dyno/emissions. It's an auto.....

Nobody seen this?

Well, it has been 5 months and it happened again. Since I don't have all the diagnostics gear listed above, does anyone have a "simplified" home-garage mechanic test or repair?

Happened again today

So at lunch the car cranked but no start. turned key off, retried, fired right up w/CEL. Drove car a couple of miles down the highway and it ran fine, but would not upshift into 4th (auto). Pulled over, cleared the P0725 CEL (engine speed sensor circuit) and car shifted as usual.

Strangest thing is that the car seemed to run smoother before I cleared the CEL. Afterwards, it was back to its little bit hinky shifting pattern (148K on original 01M)

So, where is the engine speed sensor located and is it easy to access/change?