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USA emissions testing -obd2 plug

Discussion in 'General Discussion' started by Desmond, May 20, 2019.

  1. As an automotive electrician in New Zealand I'm interested to know about how emissions tests are carried out in the USA. From what I have seen on many obd2 scan tools there is an I/M readiness button which gets into the vehicle's computer and checks to see if the computer is happy with all the engine system's operations.
    In NZ we get all sorts of vehicles, a large proportion are not obd2 compatible but the numbers are increasing. We get a lot of used Japanese vehicles and they only went full obd2 in 2006.
    Apparently the obd2 plug has to be within reach of the driver so when a cop pulls you over you are able to plug the scan tool in without getting out of your vehicle.
    My question is - do they just do an I/M readiness check [which shows an image as per the attached picture] to make their decision?
    Very interested in knowing this for my upcoming ebook :) 

    Subscribe to see EXIF info for this image (if available)
  2. Not sure about the rest of the US, but in the state of Georgia, a cop would not be using the scan tool.

    The only person that I’ve seen use one is the mechanic/station when getting my yearly inspection certificate. They simply check that the emissions system working correctly then print/submit the certificate to the state. ($20 - $30) yearly fee.

    I’m sure that the dealership and other auto mechanics use the tool when analyzing a vehicles system or determining if any error codes have been kicked.
  3. I used to drive a VW diesel. :eek: 
    Now, I drive a gasoline powered one. I also live in Idaho, and the only part of the state that tests for emissions is the Capitol, Boise. That happens when your plates (tags) need to be renewed, usually every 2 years.
  4. Hmmmm, thanks - maybe it's Europe that does that then?
  5. And California, I believe.
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  6. I know of no state in the US that does roadside emissions testing (with the possible exception of spot checks done on commercial vehicles when they are stopped to check safety gear, compliance with load limits and proper driver paperwork) and certainly not with an OBD port reader. It is pretty useless for that task. It can read most if not all the stored parameters in the vehicles control computer (ECM/PCM) and some can display many parameters dynamically (while the engine is running).

    Some states use roadside sensors to detect emissions levels.

    An OBD2 reader is a handy diagnostic tool but not very useful for determining compliance with emissions regulations.
  7. It can't tell the exact exhaust emissions but if one of the internal monitors isn't 'ready' then the vehicle will not meet its emissions so it does have its uses.
  8. kilofoxtrott

    kilofoxtrott European Ambassador Moderator

    Dec 29, 2011
    Tettnang, Germany
    In Germany it's done every 2 years (3 years when the car is new) at the official technical inspection (TÜV).
    You'll get a tag on the rear license plate then. The whole inspection costs about € 100.

    Police is not controlling it, but can send a car to the inspection.

    • Like Like x 1
  9. I live in CA! The most emissions-obsessed state in the Union! I've never heard of roadside emissions testing, nor of a law officer using one of those scanners. First of all, in order to pull a driver over, the officer would have to have reasonable cause... and in that case, emissions would likely be the LAST thing they'd be thinking of. They'd be more likely to write you up for a fixit for no front plate or a burnt out bulb...

    The largest cause of smog-check (emissions) failures is going in with the check-engine light on. That's an automatic fail. Pretty much anything else passes, unless the vehicle is belching smoke as you pull up to the test station. My dad has an '87 Ford Econoline conversion van that's on its last legs. He is require to take it to a smog-test only station. The tester tests it, tells him to drive another 30 miles to warm it up, and bring it back... it passes. Hmmm.

    A new vehicle is exempt from smog-checks for the first 5 yrs. Then it's every other year on a regular basis.
    • Like Like x 1
  10. barry lloyd

    barry lloyd

    Jun 12, 2007
    In the UK we have an M.O.T ( Ministry of Transport) test when the car is 3 years old and every year after that. This includes emissions- tyres - lights-horn- seat belts- window wipers - general body condition - wheel alignment- brakes-etc etc. Police can also do a roadside check if they think something needs looking at, that has to be done by a qualified officer. The number plate stays on the vehicle from new unless a private plate is purchased. I actually do have one and I transfer it for £80 when i get a new car.
    Fail the MOT and the car is off the road until the faults are fixed within a time limit

    On my Nissan Xtrail Tekna
    Subscribe to see EXIF info for this image (if available)

    Not only did we have 3 dogs at the time but also owners of a boarding kennels and the B is the initial of my name
    Number plates have to be older than the vehicle if private ones and no "show" plates allowed on the road. Also letters/numbers have to be properly spaced and shown in yellow with black letters/numbers on the back
    Bought this plate way back in around 1996 when it came back on the market (1964 plate first released) and been on several cars since then. Also value increase considerably since purchased. Now very hard if not impossible to get B reg plates like this let alone single number and word.
    Last edited: May 21, 2019
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