When do u change the cambelt on a audi 4 2.5 diesel convertable 2005

BEST GUESS WOULD BE BELT IS OFF A TOOTH , BUT FIRST YOU NEED CODE FOR WHY LIGHT IS ON THE YOU CAN BETTER FIX ISSUE

not so sure what a cambelt is, but it would have a timing belt.
Best regards
Ck

A diesel uses a different procedure. You'll need a tool to hold the camshaft pulley parallel to the top of the cylinder head. The timing mark to set TDC for piston #1 is located on top of bell housing. The pointer must be aligned on the diamond cut on the flywheel. A VW/Audi setting bar tool #2065A is needed to lock the camshaft in position. Lock the injection pumpin position using the special lock pin (VW/Audi special tool no. 2064). Caution: If the drive belt is broken or has jumped time, do not attempt to lock the sprocket at this time!!! You will also need VW/Audi special tool no. VW210 to measure belt tension between camshaft sproket and injection pump sprocket. So good luck.

My 2005 A4 3.0 convertible audi is not a diesel, but I had a similar experience with a low oil signal going on and after checking the oil, which was sufficient, and replacing the dipstick, the light did not come back on until a subsequent trip. The light usualIy went on when I was close to the needing an oil change. I've had the car, a used one, for about two years, and the oil light minimum signal started behaving like yours early. About a week ago the oil pressure warning light came on. I don't know if there's a relationship, but if there is be careful. Audis of our vintage have a problem with sludge build up that damages the oil pump, which is a costly item. If you drive the car with low oil pressure you may seriously/fatally damage the car. I don't know if the sludge, if that's what you have, can be cleaned out, but I'd do it if it can be. My mechanic advised me to trade the car to a dealer rather than fix it. Hope you have better luck!

55,000 miles recommended if already changed the original one

Audi 1.9 TDI and 2.0 TDI engines with pump-nozzle injection system, (year 2005 included), don't have permission to run with Bio fuel !!!
First you must replace fuel filter, interflow a quality Diesel additive (for 60 liters Diesel fuel dosage) fill up tank with Diesel fuel and run at least 300 km on highway at 3000-3500 rpm in 4-th gear.
I recommend you Foerch Diesel Reiniger System additive! I use this additive from 3 years ago and is certified on Audi TDI engines!

crank marks are on flywheel--pull the cap off on top ov the box and u will c the flywheel,turn clockwise untill pointer lines up with a punch mark on flywheel.

yhe book is 20 dollars at oriely auto but if tou have prob im here vote for me ok

usually you should do it for peugeot diesel at 122000 miles along with water pump and the tensioner roller that runs under the cambelt too. But to be on the safe side do it at 100000 and save the fortune.
It took me (DIY job) about 6-8 hours as i wanted to save 450 pounds.

There is no change interval as it is chain driven