First of all, assuming your DUI is from California and you were over 21 yrs old at the time, the code section that you violated or pled guilty to in 2006 is from the Vehicle Code, not the Penal Code. It was likely Vehicle Code section 23152(a) [driving under the influence of alcohol or drugs or any combination thereof] or 23152(b) [driving with a BAC of .08% or more]. If there was accident and someone was injured, then it could have been VC23153(a)/(b). An expungement falls with the purview of Penal Code section 1203.4. There would have possibly been a punsishment enhancement pursuant to VC23578 for having a BAC above .15% and pursuant to VC23538 for having a BAC of .20%.
Usually in a DUI case, you will be charged with two separate criminal offenses: Section 23152 (a) of the California Vehicle Code, driving under the influence; and, Section 23152 (b) of the California Vehicle Code, driving with a blood alcohol level of .08% or higher.
Section 23152 (a) is driving under the influence. The offense is basically defined under California law as “driving a vehicle while you are under the influence of any alcoholic beverage and/or a drug.” The essence of the offense is that you were unable to safely operate your vehicle because you were impaired due to alcohol and/or drugs. Please keep in mind that a charge of “driving under the influence” is not the same thing as “drunk driving.” You do not have to be drunk in order to be convicted of driving under the influence.
Section 23152 (b) is defined as “driving at or above the legal blood alcohol limit of 0.08%.” This offense is different than the (a) count above in that it does not matter how well or poorly you were driving the vehicle, just that you were at or above the limit.
You can only be punished for one of the crimes listed above because your actions only constituted one continuous act.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.