A6 5-cylinder. TDI won't start

Hi,

Audi A6 with a 5-cylinder AEL engine from 1997, exhibiting the following issues:

Started the car this morning, and after about 300 meters, there was a loud bang, the engine stopped, and the oil pressure warning light came on.

After a startup process, the error log shows 'Speed sensor / intermittent'.

Could that be the cause?
When I try to start it, it makes a cheerful sound, and occasionally there's a slight sign that it wants to start, and there's always a small puff of white smoke coming from the exhaust.

We checked the front and rear timing belts, the air mass meter flap for smooth operation, the shut-off valve on the ESP, and the air intake hoses.

When measuring the sensor with an ohmmeter, it should read 1 kOhm, and a reading of approximately 0.995 kOhm would likely be acceptable. Upon starting, the display should show the engine speed, which should be around 30 RPM in idle. During our startup attempts, the values ranged between 8 and 16. Is that sufficient?

Or is it simply due to the speed sensor? But what did Madam hear as a loud noise?

Deleted as requested.

Hi,
You checked the timing belts. How about the timing? Could the front belt have jumped a tooth? In my case, the rear camshaft sprocket has a notch that, helpfully, points straight up when the engine is at top dead center, aligned with a rib on the cylinder head. That doesn't necessarily have to be the case with your car.