We'd first recommend you revisit the smog station which performed the initial repairs and explain the fact that your GMC Yukon's check engine light has re-illuminated after just two days. If repairs were done properly, and assuming all the repairs required to get the check engine light to turn off were performed, they must go back to diagnosis and find the actual fault(s) which is causing the malfunction. They should accommodate you with some sort of credit if in fact their initial diagnosis was inaccurate/incomplete.
They might find that the initial repair(s) were required and that further repair(s) are needed. If this is the case, then yes, you may apply for CAP and have additional repairs performed with the financial assistance of the State. Assuming this particular smog station is a STAR certified test & repair center, you may choose to continue repairs at this facility.
