Vectra C estate 2003 2.0 dti.

When motorway driving I keep getting the spannner light showing. This only happens when I need to slightly accelerate to negotiate an incline or overtake. Engine doesn't go into limp mode and turning off then on the ignition clears the light.

I have had the fault code read and below is listed the results.

P0638 Throttle Present
( 5A ) Control circuit

After researching on this forum I have removed and thoroughly cleaned out the Throttle Butterfly Assembly.

I have replaced
ALL the vacuum pipes with silicone piping and checked the boost pipes for splits.

However the problem remains .

Does anyone have any suggestions as to what to look for next?
Many thanks in advance.