Note: costs mentioned below are given in US dollars as a general point of reference — actual prices vary by country, currency, and local market.
Most inspection failures come down to five things: a burned-out bulb, worn wiper blades, low tread depth, a cracked windshield in the driver's sightline, and a lingering check-engine light. Walk around the car checking every light with the engine running, run a coin test on tread depth (less than 2/32 in. fails almost everywhere), and make sure any warning lights have been off for at least one full drive cycle before test day. A $20-$40 pre-inspection check at an independent shop is cheap insurance against a failed test and a second inspection fee.
At a glance
| Check item | Typical pass threshold |
|---|---|
| Tire tread depth | 2/32 in. (1.6 mm) minimum |
| Windshield cracks | None inside the wiper sweep/driver sightline |
| Brake pad thickness | Usually 3-4 mm minimum |
| Check-engine/warning lights | Off, no active codes |
| Exterior lights | All bulbs functional, correct color/lens |
Why so many cars fail on small items
Inspection programs — whether a US state safety/emissions check, a UK MOT, or a similar roadworthiness scheme elsewhere — are built around the cheap, frequently-neglected parts of a car: bulbs, wipers, tires, and fluid leaks. Independent shop surveys and testing-agency data consistently show that lighting failures and worn tires are among the top reasons cars get turned away, not major mechanical faults. That's good news, because almost everything on this list is a DIY fix in under an hour.
The walk-around: lights, glass, wipers
- Turn the key to "on" and walk the car checking headlights (low/high beam), taillights, brake lights, turn signals, reverse lights, and the license plate light.
- Have a second person tap the brake pedal while you check brake lights, or back the car up to a reflective garage door.
- Inspect the windshield for chips or cracks longer than about 1 inch, especially in the driver's direct sightline — these are an automatic fail in most jurisdictions.
- Replace wiper blades if they streak, skip, or are visibly cracked; blades typically last 6-12 months depending on climate.
Tires, brakes, and suspension
Use a tread depth gauge or the reverse-Lincoln-penny test on all four tires, including the spare if it's part of the inspection. Look for uneven wear patterns (cupping, feathering, or wear concentrated on one edge), which can indicate an alignment or suspension issue that may also flag during inspection. If you can hear grinding or feel pulsing through the brake pedal, get pads and rotors checked before test day rather than after a failure.
Fluids, leaks, and the exhaust system
Pop the hood and look under the car overnight for fresh drips — oil, coolant, or transmission fluid leaks are common fail points. A rattling or unusually loud exhaust often means a failed weld or a loose heat shield, both inexpensive fixes at a muffler shop. Top off washer fluid, coolant, and oil to their marked levels.
Clear the check-engine light the right way
Simply disconnecting the battery to clear a check-engine light can cause an automatic fail. Most emissions tests check the vehicle's "readiness monitors," and disconnecting the battery resets them to "not ready," which some test systems reject just as harshly as an active fault code. If you have a code, get it diagnosed and actually fixed, then drive at least 50-100 miles of mixed city/highway driving to let the monitors reset naturally before your test.
If a warning light comes on and then goes off on its own, don't assume it's fine — intermittent codes are still stored and can resurface during testing. A $15-$25 code reader or a quick scan at most auto parts stores (often free) will tell you what's stored before you commit to a test appointment.
Day-of checklist
- Wash the car so the license plate and lights are clearly visible.
- Remove clutter that blocks the inspector's view of the VIN or dashboard.
- Bring registration, proof of insurance, and prior inspection paperwork if required locally.
- Arrive with at least a quarter tank of fuel — some emissions tests need the engine running for several minutes.
Frequently asked questions
What are the most common reasons cars fail inspection?
Can I drive with a check-engine light on to get to my inspection?
How much tread depth do I need to pass?
Will a small windshield chip fail an inspection?
How long before my inspection should I do this checklist?
Sources & further reading
Figures, prices and policy details were current at the last-updated date above. Automotive pricing, incentives and regulations change frequently — verify time-sensitive details with the linked primary sources. Read our editorial policy and fact-checking standards.
