w124 1989 300E 250K km's error code 20
 

Engine running at operating temp, getting error code 20 (constant 19%)
Using pins 2 and 3... the official explanation from the w124 CD...
'Full load contact incorrectly connected or faulty. 20% readout only if throttle valve switch (S29/2) operated.'

S29/2 = throttle valve switch.
Throttle Valve Switch.... is this part available seperately, or is it connected to the throttle body and that is the only way it can be fixed/replaced. I haven't been able to find one in any of the online spares dept's. (TVS that is)
Anyone else been down this road.?