Any interlock violation is a concern, especially for a felony, but these circumstances often occur, so the judge probably won't be hard on you. The judge is going to have trouble understanding how-after 18 months without a problem-you would use a mouthwash with alcohol in it. Be much for careful in the future. This will probably delay you getting the interlock removed.
You are fortunate that you blew again after 45 minutes. If alcohol was absent from the second test, you have a fighting chances. Mouth alcohol normally disappears after 15 minutes, but your body does not eliminate alcohol that quickly. The short time frame would be indicative of mouth alcohol and not consumed alcohol. If the Judge is able to look past this alleged violation, you need to make sure that you do not have any other problems as the Court may watch you closer now. If you have an attorney, I recommend that you contact you attorney and they can advise you further.
Definitely tell you PO, you gain points by honestly admitting possible violations. This makes you look trustworthy and they are more likely to believe you.
In my experience many people will have one or two innocent slip-ups which the provider may not think of as a "violation" to report to the probation office.
If you have had many violations, you should consult your attorney. Each judge is different in their level of tolerance, so my advice should be regarded as general and not specific to your problem.
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