Hello dear customer, i am back. Sorry for my delay i had to go out to solve an issue an it took more time than i thought.
The code U0121 is regarding to ABS, so this does not cause the vehicle to not turn on.
The codes P0203 and P0202 are faults in injectors 2 and 3, but I think we should proceed first to correct first the code P0341 iwhich is the one that is causing the vehicle not to turn on, this code indicates a problem in the reading of the camshaft sensor, it is not synchronized or it is not detectecting the synchronize with respect to the crankshaft, this happens for various reasons that I will try to cover in my explanation.
As you told me the timing is right, so I would be look for an electrical fault, but before I would like that you to indicate if you have replaced the camshaft and the whole timing kit, including the gears.
If so, the camshaft sensor may be defective, as you indicated to me the CKP sensor was replaced so it is okay that we do not proceed to replace it.
If these sensors are correct and working as usual
We must proceed to check the wire branch and its connectors on both sensors. Also check when the chamber or cylinder head was disassembled, it did not pull the wire branch, causing the connectors to came out of their place or a cable to split.
Also check the that computer has not had any mishap when trying to start the vehicle.
In addition, it may happen that the crown where the crankshaft sensor receives the reading (The crown is that gear where the CKP is reading the time) has some defect
As you see, there are several factors that would be altered and you should review.