P0726 Engine Speed Sensor

kg1992

New member
Joined
Oct 13, 2020
Location
Edmonton, AB
TDI
2005 Passat BHW Sedan, 2005 Passat BHW Wagon
Ok,
I have a 2005 BHW Passat wagon that I am trying to diagnose. I originally bought it for the turbo for my 2005 BHW sedan, however it is in much better shape and I have been trying to make it run. The previous owner said it ran fine till he hit a pothole and it stalled.

It consistently throws P0726 "engine speed circuit" code, every time I try to start it. I have replaced the crank sensor, with no change in symptoms.

I tested the voltage on the crank sensor harness and it is the same as my other car.

When I try to start the car it fires 3-5 times and the tach jumps up to ~200rpm then the tach drops off, the engine continues to crank but not fire and the glow plug light starts to flash. The motor cuts all power to the injectors in the process.

Now I am leaning toward the possibility that:

A) the toothed gear in the crank has somehow been misaligned from the sensor
B) the wiring harness has some chaffing (did look at the wires between the crank harness and ECU (what a mess) but did not notice anything
C) the ecu has failed.

any thoughts?

I tried Swapping the ECUs between my 2 cars with the following result:

The running car will not start with the ecu from the problem car, the problem car will not start with either of the ECU. (Immobilizer? OR vin specific? I dont know)

Are there any OBD readers that will provide the cam pulses available to the public?, my fathers one does not.
 

Mozambiquer

Veteran Member
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI
Your best bet would be to use an oscilloscope and scope the crank sensor signal. That may tell you something. Another possibility could be that it jumped timing.
 
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