What can you check yourself before Japan's shaken inspection?

Shaken (車検) is Japan's mandatory periodic vehicle inspection. A new private passenger car is inspected after three years, then every two years. The inspection checks that the car meets the national safety standards: brakes, lights, tyres, steering, exhaust and emissions, the underbody, warning lights and more. Prices vary by shop, so this post does not quote any.

Most of the preparation is routine. The warning lights are the part people tend to overlook.

A lit warning light means the car will not pass

Since February 2017, a lit engine, brake, ABS or airbag (SRS) warning light on the instrument cluster means the car fails shaken until the cause is fixed.

In most cases a warning light comes on because the car has stored a fault code. That code says what is wrong, and you can read it yourself before you take the car to a shop.

OBD inspection: the car's stored codes are checked too

Since October 2024, shaken has included an OBD inspection. It covers new passenger car, bus and truck models approved from October 2021 onward. For imported cars it covers new models from 2022 onward and has applied since October 2025. At inspection, the inspector connects to the OBD port and reads 特定DTC: fault codes that mean a system such as ABS, stability control, automatic emergency braking or the emissions equipment no longer meets the safety standards. If one is found, the car fails.

In plain terms, the codes the car has stored now matter at inspection, not only whether the light happens to be off.

A pre-inspection checklist

Go through this list a few weeks before the appointment, so any problem can be fixed without time pressure. Most items take a few minutes, and none of them needs special tools. Anything you are unsure about is worth raising with the shop when you book.

• Lights: headlights, brake lights, indicators and reversing lights all working
• Tyres: tread depth, pressure, cracks
• Wipers and washer fluid: clean wiping, working spray
• Horn: sounds properly
• Brakes: pad thickness and brake fluid
• Exhaust: no corrosion, unusual noise or leaks in the muffler and pipes
• Warning lights: engine, brake, ABS and SRS all off
• No illegal modifications
• Paperwork: compulsory insurance (自賠責) still valid, tax payment certificate (納税証明) ready if your shop asks for it

Codes that commonly stand in the way

These are common causes behind a lit engine warning light:

• P0420: catalyst efficiency below threshold. Often a worn converter, but an exhaust leak near the sensors or an engine fault such as a misfire can cause it too.
• P0171: fuel mixture too lean, often from an air leak.
• P0300: random misfire, pointing to ignition or fuel problems.
• P0455 and P0442: leaks in the evaporative (EVAP) system. The most common cause is a loose or worn fuel cap.

Why check before the shop, not at it

If a warning light is already on, the car cannot pass, and you have to come back after the repair. Knowing the code beforehand lets you ask the right question, get a quote for the real problem and decide whether it is something you can handle yourself, such as a loose fuel cap, or something that needs a workshop.

It also helps to know what is stored but not lit. A fault can be recorded without the light staying on, and on cars covered by OBD inspection some of those stored codes are now checked. Looking a few weeks ahead leaves time to repair the cause properly, rather than rushing a part on the day.

Reading the codes with OBD DashX

With an ELM327 Bluetooth adapter, the Android app OBD DashX can read the fault codes behind the warning light. It covers the engine, ABS, SRS and other systems, as far as your car responds. Each code is explained on this site, including in Japanese. Reading codes is free, and clearing them is a one-time in-app purchase. The app's screens are in English.

The order matters. If you clear a code without fixing the cause, the light comes back and the car still will not pass.

• First, read the codes in the app and find out what needs fixing.
• Next, fix the cause.
• Last, clear the codes and confirm the warning light stays off.

OBD DashX does not perform shaken and does not replace it. It does not read 特定DTC in the legal sense either. It is a way to know the state of your car before inspection day.

If you want to check your codes before shaken, try OBD DashX.