The brief
The Touran had gone lazy off the line, the response from a stop felt a beat slower than it should, and a check engine light had come on. Not what a family wants from the car that does the school run, so it came in for a proper look.
The throttle body is the valve that meters air into the engine, opened by a little electric motor that takes its orders from the pedal. When that motor and the position sensors inside the throttle body start to fail, the valve doesn't track its commands cleanly, so the engine gets the wrong amount of air at the wrong moment, which is the lazy, hesitant feel off the line, and the engine computer sees the mismatch and flags it.
The diagnosis
Live data on the scanner showed the throttle butterfly tracking jerkily through its commanded range rather than following it smoothly, and the codes pointed at the throttle valve control and its position sensors. A clean of the throttle body at an earlier service had helped only briefly, which fit: the actuator itself was failing, not just a carbon build-up.
That made it a throttle body replacement. You don't rebuild the actuator, so the unit gets changed.
The work
The intake hose came off, the throttle body was unbolted, and a new VAG-spec unit fitted in its place, the harness reconnected. Then the throttle adaptation routine was run on the scanner so the ECU learned the new closed and full-open positions, and the stored codes cleared.
A road test confirmed the response was sharp again from a standing start.
The outcome
Steady idle, sharp response from a standing start, and no check engine light returning after a drive cycle.
The Touran went home running cleanly through the rev range. A failing throttle body only gets jerkier, and on a family car you want it crisp at every junction, so swapping the unit and relearning the positions put the throttle response right back.