VW T5 Transporter 2.5 TDI AXD engine.
Problems: Engine wouldn’t start but the engine would crank over fine.
We started with a full auto scan this showed a fault code off – 16725 – Camshaft Position Sensor (G40) – P0341 – 000 – Implausible Signal. We inspected the engine and could see the cylinder head looked very new (A quick call with the customer informed us – a recondition engine had been fitted and had never run from having a recondition engine fitted)
We started with the fault code it stating camshaft position sensor G40 000 – Implausible Signal – The implausible signal is important this to me, this is saying the ECU is happy with the resistance and doesn’t feel it shorted to plus or ground so I’m guessing the sensor is good but it not getting the correct signal out. I’m going to start by using the picosocpe to take a measurement from the sensor I will also take a feed from the crank sensor G28
The readings look good, the crank G28 (Blue) is giving and good signal and the camshaft G40 is being pulled upto 5V in a pattern would expect to see. To make sure the reading are correct we have a 2.5 TDI works van we decided to take the same reading from our van.
As you can see the blue line are bigger this is because the work van is idling and the faulty van was cranking. If you compare the 2 pictures you can now see the problem. Going from the crank reference point (the gap in the regular pattern) there are 58 lower peaks and I’m guessing the gap is 2 teeth wide so it would use a 58-2 crank wheel (60 teeth with 2 missing teeth). For every 360 deg revolution off the crank there is 60 trigger points. 360/60 = 6 every lower peak = 6 deg.
On the faulty van the first cam trigger after the reference is 8.5 lower peaks, so the cam trigger is 51 deg after reference point.
On the good van the first cam trigger after the reference is 7 lower peaks, so the cam trigger is 42 deg after reference point.
This proves the cam timing is out on the faulty van and why the engine management system is stopping the engine from starting. As the engine is gear driven and would guess at most gears being around 36 teeth (36 teeth = 10 deg per tooth) So I would guess the cam timing is 1 tooth out.
With this information the van was recovered by the reconditioning company and they sorted the engine timing out.