C4 GP MK2 juddering on hills

[Mazzy7126]

I was wondering if anyone can confirm if these codes would correspond to the symptoms.

My Dad's 2016 C4GP about 60k on clock. It has recently started sounding a little rough. Drive ok on the flat/downhill but has to be dtopped down to 2nd on steep hills that it was previously able to drive in 2nd gear. If you are in 3rd gear the car judders.
It had no obvious fault codes initially on running a diagnostic. There was a lose relay so that was reinserted but nothing obvious engine wise.
Tested again on a hill and a fault flashed up on the dashboard. Ran diagnostics and it came up with p2084 and p0426.
Would these likely cause the symptoms?
Vin is VF7**************[VIN obfuscated, can be read by forum staff]

[PaulC5]

A search suggests exhaust temperature sensor(s) is(are) faulty or wiring which could be putting the car in limp mode. Also check the exhaust for leaks.
P2084-00 - Exhaust Gas Temperature Sensor Circuit ... P0426-00 - Catalyst Temperature Sensor Circuit Performance Bank 1 Sensor 1