M3 1.5DCI: Fault emission system DTC P0201 & B1231

My Megane 3 yesterday, after 100 meters of full-gas drive, launched the hill up the engine control light. Error exhaust system. I was unable to perceive a change in driving behaviour, gas acceptance, jerking. I was able to read the following 2 codes per OBD2: P0201 – Injection valve cylinder 1 (short circuit/undercalculation in the circuit) B1231 – AGR insufficient flow, probably also indicates external voltage, values are unplausible for the ECU. The troubleshooting tips usually apply to the wire harness/plugs. Possibly alternator overvoltage, air flow meter, or the injector directly. I have first deleted the error and will test again. As said, I felt nothing. No emergency running program etc. And then into the workshop. Do you know the error picture? Do you have any ideas? Maybe the Renault specs like Daswara? Thanks first. I will report a lot. Greetings faleX