EGT Sensor 4 (G648) Replacement & Connector Location - 1.6 TDI DDYA (Octavia Mk3)

Hi everyone,

I own a 2017 Skoda Octavia 1.6 TDI (85kW, engine code DDYA, DSG).

I am experiencing a weird issue where the car loses power (cuts boost/derates) only under load — specifically when driving uphill in hot weather, with the AC turned on, or right in the middle of a DPF regeneration. There are no warning lights on the dashboard.

I scanned it with VCDS, and "Particulate filter output: temp. sensor 1" (which should be EGT Sensor 4 / G648) is permanently stuck at -40.0 °C and 0.000 V.

I managed to locate the sensor by reaching deep behind the engine block and took the attached photo. It is screwed right into the exhaust elbow at the very bottom/outlet of the DPF, just before the flexi pipe.

Since I don't have access to a professional car lift or a pit at the moment, I have two questions:

1. Where exactly does the cable for this sensor route and where is the connector (plug) located? Is it clipped underneath the car on the subframe/tunnel, or does it route upwards to a connector station behind the engine block?

2. Can this sensor be replaced entirely from above (through the engine bay)? Unscrewing the sensor itself seems doable from the top, but I'm not sure if I can unclip the wiring harness and reach the plug without getting under the car.

Any advice, diagram, or workshop manual screenshot would be highly appreciated!

Thanks in advance!