If you fail an ignition interlock test, the vehicle won’t start, the failure is logged in a tamper-resistant record, and that record is reported to whoever is monitoring your case: a court, a probation officer, or your state’s motor vehicle department. The device flags breath alcohol as low as 0.02%, so the trigger can be anything from actual drinking to mouthwash used minutes earlier. What happens next depends on when the failure occurred, how many you’ve had, and the rules of your state’s program. Consequences run from a short lockout to extra months on the device, a revoked restricted license, or new criminal charges for tampering.1National Highway Traffic Safety Administration. Ignition Interlocks – What You Need to Know
What the Device Does the Moment You Fail
If you fail the startup test, the vehicle simply won’t start. The device enters a temporary lockout, usually a few minutes on a first attempt, that blocks you from immediately retesting. In many states the lockout grows longer with each consecutive failure. Rinse with water, wait out the lockout, and blow clean, and the car will start. Every failed attempt is still logged, pass or no pass afterward.
If you fail a rolling retest while driving, the engine does not shut off. Cutting power to a moving vehicle would be dangerous, so the device logs the failure and sets off the horn and lights as a persistent alarm until you pull over and turn off the ignition. Once the engine is off, the same lockout cycle kicks in.
After a certain number of violations in a short span, many devices enter a permanent lockout. The vehicle will not start at all until you bring it to a service center for a manual reset, which comes with its own fee on top of whatever legal consequences follow. The exact count that triggers a permanent lockout varies by state and manufacturer.
What Counts as a Failed Test
A violation falls into one of three categories, and each is recorded the same way.
- Startup failure: you blow before driving and the reading meets or exceeds the preset limit, typically 0.02%.
- Rolling retest failure: while the vehicle is running, the device prompts you for another sample at random intervals, giving you somewhere between 3 and 15 minutes depending on the state to safely pull over and blow. Missing that window or blowing over the limit counts as a failure.
- Tampering or circumvention: having someone else blow for you, disconnecting the device, push-starting the vehicle to bypass it, or introducing an altered sample. Monitoring authorities treat these as positive readings and often impose harsher penalties.
How the Failure Reaches Your Monitoring Authority
Every interaction is recorded in a tamper-resistant data log that captures the breath sample, the reading, the date and time, and whether the test was a pass, fail, or skip. Many states also require a camera that photographs whoever is blowing, which both prevents substitution and gives you evidence if a disputed test wasn’t you.
The data reaches your monitoring authority one of two ways. At your mandatory calibration appointment, the service provider downloads the log and sends a compliance report. Those appointments run every 30 to 90 days depending on your state. The federal model specifications require the device to hold calibration for at least 30 days, with a 7-day countdown warning before it locks you out entirely for a missed service.2Federal Register. Model Specifications for Breath Alcohol Ignition Interlock Devices Some states and providers use real-time wireless reporting that can notify a probation officer or the DMV within minutes.
Missing the calibration appointment is itself treated as a violation in most programs. Once the 7-day grace period expires, the device locks the vehicle and the missed appointment shows up on your compliance record with the same weight as a failed breath test.
Legal Consequences After the Failure Is Reported
What follows depends on the type of violation, how many you’ve had, and your state’s program rules. A single borderline reading followed by a clean retest is treated very differently from repeated high readings or evidence of tampering.
Extra Time on the Interlock
The most common consequence is more time with the device. A violation can add months to your required period, and in some states the clock resets, meaning you need a fresh stretch of violation-free days before you’re eligible for removal. Over 30 states use compliance-based removal, where the device only comes off after a set number of consecutive clean days.3Governors Highway Safety Association. Study Finds Ignition Interlock Compliance-Based Removal Laws Help Reduce Drunk Driving Repeat A single failure late in your program can erase months of clean compliance and restart that countdown.
Revocation of a Restricted License
If you’re driving on a restricted interlock license, a reported violation can get that license revoked. In many states this is an administrative action handled by the DMV based solely on data from your device provider, with no separate court proceeding. Losing the restricted license means you can’t legally drive at all until the revocation is resolved, which usually involves a hearing and sometimes additional conditions before reinstatement.
Probation Violations and New Charges
For drivers whose interlock was ordered as a condition of probation, a failed test can trigger a probation violation hearing. A judge can impose fines, mandatory substance abuse treatment, community service, or jail time. Tampering carries the steepest consequences. Most states classify it as a misdemeanor, with penalties that can include up to 18 months of imprisonment and fines of several thousand dollars depending on the jurisdiction.
What a Failure Costs Beyond the Courtroom
The device itself is already an ongoing expense: installation around $70 to $150, monthly lease and monitoring fees of roughly $50 to $120, and about $25 per calibration visit. An unscheduled reset after a permanent lockout costs more. A violation that extends the program adds proportionally to the total.
The insurance side is often the larger hit. Most states require an SR-22 or FR-44 certificate of financial responsibility to keep your license after a DUI, usually for a minimum of three years from the conviction date. A new violation during the interlock period signals continued risk to your insurer, which can mean further rate increases or an outright cancellation, pushing you into the high-risk market where premiums can run several times standard coverage.
Everyday Things That Can Trigger a False Reading
Because the device flags breath alcohol at just 0.02%, a number of common products and foods can produce a reading you didn’t expect. This is where most avoidable violations happen.
- Mouthwash and breath sprays, many of which contain alcohol above 20%.
- Alcohol-based hand sanitizer used right before testing.
- Fermented or yeast-heavy foods: ripe fruit, bread straight from the oven, energy drinks, kombucha, dishes made with red wine vinegar.
- Non-alcoholic beer and wine, which can carry trace amounts despite 0.0% or 0.5% labeling.
- Certain asthma inhalers and liquid medications that use alcohol as a carrier.
- Cigarettes, which produce acetaldehyde, a compound the sensor can read as alcohol.
The practical fix is to rinse your mouth with water and wait a few minutes before testing. If you fail a startup and believe it was a false positive, waiting out the lockout and retesting with a clean mouth usually resolves it on the spot. The device logs both the failure and the clean follow-up, which helps if the sequence is later reviewed.
Disputing a False Positive
Not every failed test means you were drinking, and the system has some built-in protections for that. A startup failure followed by a clean retest a few minutes later shows a pattern consistent with mouth contamination rather than intoxication. Most monitoring authorities review the full sequence of readings, not isolated failures.
If you get a failure you believe came from food, medication, or another substance, a few steps matter immediately:
- Rinse and retest. Swish water and blow again as soon as the lockout allows. A clean follow-up on the same log is the strongest evidence of a false positive.
- Write down what you ate, drank, or used before the test, and keep receipts. Some providers offer a formal incident report form where you can explain the circumstances and upload supporting documents.
- Tell your DUI attorney and your probation officer as soon as possible. Reporting proactively reads very differently from explaining a violation after it has already surfaced on a compliance review.
- Request the device data. The full log, including timestamps, BAC levels, and camera images, is available for review. If the camera confirms you were the one blowing and the retest came back clean, that combination is usually enough to resolve a disputed reading.
Cameras help here in particular. A photo confirming it was you, paired with a clean retest, leaves a straightforward paper trail showing contamination rather than consumption. States that require camera-equipped devices cite this dispute-resolution benefit as part of the reason.