OBD-2 cables FTW. Also got one, a USB jobby and Multi ECU scan. Allows me to kick off the DPF regen before emissions test (thus prolonging the vehicle life and wallet contents) and kill the service indicator every time I don't get it serviced
med6573's one is a rather nicely engineered bit of kit though. I haven't cracked mine open but it's probably got bugger all in it.
On this side of the pond annual inspections, and what it entails, is left to each state to decide. California is the strictest state when it comes to emissions testing and there are some states that have no testing of either safety or emissions. I reside in New York State and we have an annual “Safety and Emissions Inspection”. The vehicle is checked for tires, brakes, steering, lights, etc. If the vehicle is 1996 or newer the ECU is linked on line to DMV (Dept of Motor Vehicles) and scanned for current and pending DTC's. If any are found it's an automatic fail. Even if it's DTC P0440 for loose fuel cap you fail. Get it fixed then test again (and pay again).
A few months ago the Honda Civic starting puking DTC P1457. The detail is “Evaporative check valve minor leak to atmosphere”. In other words....I had a small fuel vapor leak near the charcoal canister assembly. Horrors! I'm polluting! A bit of research revealed that this is a fairly common problem in older Hondas. The evap valve and the canister are located under the vehicle by the fuel tank, exposed to the elements. The evap valve rusts and develops pin hole leaks. And individuals reported that shops and dealers charged upwards of $500 USD to fix it. So a few weeks ago I got under the Civic and checked this valve. Sure enough, it was rusted. I ordered a new valve and canister assembly. About $150 USD in parts. 1.5 hours of my labor (cheap) and the new parts were installed. Reset the DTC and drove it for a week to make sure it was fixed. It was. Last Wednesday it passed it's annual inspection with no issues. That scan tool paid for itself again.
Federal Regulations over here are (or at least WERE, before Resident Chump put an imbecile at the head of the EPA specifically chosen to destroy the agency) making certain minimum requirements mandatory for all state safety inspections; among them being REQUIRED to actively inspect for and seek out circumvented and damaged emissions-control hardware, and to connect to the car and make sure that aside from not having any current codes, the car is actually operating in closed loop mode and has completed all I/M Readiness tests, (meaning that the computer can confirm that it hasn't had a recurring DTC erased just before being taken to the inspection station) and that the vehicle you're inspecting has the same VIN as your paperwork and that the VIN in the computer is the same.
This was supposed to be part of the nationwide OBDIII rollout; that of course has been pretty much mulched by every lobbyist for every corporate interest you can think of (and some you haven't even imagined) for the last decade and a half. It's probably a good thing; one of the core concepts the lobbyists crammed into OBDIII (A truly misguided concept, IMO) is that every car's emission system should be remotely monitored... which for a host of reasons is just plain stupid, not just the obvious right-to-privacy issues.
Nonetheless... if your state hasn't already implemented these minimum emissions tests, they ARE coming soon. Get ready.
mnem
If you think the EPA is the enemy, you are part of the problem.