É muito pouco provável que o problema seja da manete.
As avarias mais comuns que fazem o CC não funcionar são o sensor do pedal do travão e/ou da embraiagem.
Com o VCDS podes testar estes dois sensores, assim como a própria manete.
Ao pressionares os pedais e cada botão da mante, os valores têm de alterar de 0 para 1.
Checking Cruise Control using Measuring Values - Ross-Tech Wiki
Diesel Engines
Diesel Engines often use Measuring Block group 006 to display CCS info. Refer to the charts below using line Field 2 and 4 data.
Field 2 Data
[TABLE="class: wikitable, width: 85%"]
[TR]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
1[/TD]
[TD]
0[/TD]
[TD]
0
[/TD]
[TD]
0[/TD]
[TD] 0 = Brake Not Depressed[/TD]
[TD]1 = Brake depressed (brake light switch)[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = Brake Not Depressed[/TD]
[TD]1 = Brake depressed (brake pedal switch)[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = Clutch Not Depressed[/TD]
[TD]1 = Clutch Depressed (always 0 in Auto. Trans.)[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = CCS Not active in ECM[/TD]
[TD]1 = CCS active in ECM[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] N/A[/TD]
[TD] N/A[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = CCS Switched Off TDI only *[/TD]
[TD] 1 = CCS Switched On TDI only *[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = Accel. pedal overide[/TD]
[TD]1 = CCS Operating[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = Normal CCS[/TD]
[TD]1 = Accel. pedal overide[/TD]
[/TR]
[/TABLE]
Field 4 Data
[TABLE="class: wikitable, width: 85%"]
[TR]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
0[/TD]
[TD]
1[/TD]
[TD]
1[/TD]
[TD] 0 = CCS Switched Off[/TD]
[TD]1 = CCS Switched On[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = Cancel/Off Activated[/TD]
[TD]1 = CCS Switched On[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = SET/ Decel. Not Pressed[/TD]
[TD]1 = SET/ Decel. Button Pressed[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] 0 = Resume/Accel Not Pressed[/TD]
[TD]1 = Resume/Accel Button Pressed[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] N/A[/TD]
[TD] N/A[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] N/A[/TD]
[TD] N/A[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] N/A[/TD]
[TD] N/A[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD] N/A[/TD]
[TD]N/A[/TD]
[/TR]
[/TABLE]