Hello,
it is necessary to allow pin sharing to enable selection of VREFH&VREFL pins in both ADC components. You can swicth on this feature using "Pin Sharing" menu command from selected pin´s pop-up menu. For more details please see enclosed screen-shot.
For more details about pin sharing please see CW´s help:
CodeWarrior for Microcontrollers V10.x > Processor Expert Manuals > Processor Expert Users Manual > Application Design > Configuring Components > Pin Sharing
best regards
Vojtech Filip
Processor Expert Support Team