If you have a car or truck and are not sure it will pass a smog test, an easy way to test it, is to use an OBDII scan tool with an emission check option.
While each state has its emission requirements, a compatible OBDII scan tool has built-in functions that can show if it will pass or fail most smog tests.
What OBDII Scan Tool Option is for Smog Test?
An OBDII scan tool is used to communicate with a vehicle’s onboard computer to check for errors.
Almost all cars and trucks manufactured after 1996 have an OBDII port available, usually under the dashboard.
What Is I/M Readiness?
All cars and trucks manufactured after 1996 have an OBDII port to scan the vehicles onboard computer.
Some new model vehicle models manufactured after 2010 may support two types of I/M Readiness tests.
- Since DTCs Cleared – indicates the status of the monitors since the DTCs are erased.
- This Drive Cycle – indicates the status of monitors since the beginning of the current drive cycle.
With 2010 newer vehicles emission related codes can not be cleared with a scan tool.
The codes can be read, but a drive cycle must be done for the codes to clear.
The I/M readiness gives emission-related information to see if the vehicle will pass an emission test.
The unit will give a breakdown of each component and if it has passed or failed.
This is a very handy test to have before an emission test to see if the vehicle will pass and, if not, what the problem is.
How Do I Know If a Car or Truck Will Pass an Emissions Test?
There can be no guarantee it will pass, but it is very likely to get certified.
Every state is different on smog requirements, including, in some cases, a visual inspection.
An OBDII I/M readiness test is the best home smog test check most vehicle owners can do before getting it checked at a testing station.
Many good-budget units are available, with some of our favorite picks below.
As always, be sure to read the reviews on Amazon, forums, here, or elsewhere to be sure a unit is a good fit for you.
*This post contains affiliate links.
Our Picks for Best OBDII Scan Tool for Smog Test 2023
- FOXWELL NT201
- NEXPEAK NX501 Enhanced OBDII
- INNOVA 6100P
- OTOFIX D1 Lite
FOXWELL NT201 OBD2 Scanner Check Engine Light Car Code Reader Emission Analyzer Car Diagnostic Scanner for All Cars
The FOXWELL NT201 is a low-cost OBDII scan tool with a One-Click I/M Readiness emission analyzer.
It can also scan for other OBDII codes that a car or truck may have.
Since almost all vehicles built after 1996 have an OBDII port, it works on many makes and models, including foreign and domestic.
The FOXWELL NT201 is a good budget unit that is simple to use and gets the job done.
NEXPEAK OBD2 Scanner, NX501 Enhanced OBD II Auto Code Reader, Car Diagnostic Scan Tool Vehicle Check Engine Light Analyzer for All OBDII Vehicles After 1996
The NEXPEAK NX501 is also a budget unit that works well and gives I/M readiness emission test information.
It can retrieve I/M readiness information, read and erase codes, freeze frame data, display live sensor data, Auto VIN acquisition, O2 Sensor and EVAP Test (Mode 8), Advanced On-board Monitoring
INNOVA 6100P ABS SRS Transmission OBD2 Scanner Live Data, Car Code Reader Diagnostic Scan Tool with Oil Reset /Battery Alternator Test / Full OBD II/ Repair Solutions 2 APP
The INNOVA 6100P is a good mid-range OBDII scan tool that can not only read emission information but much more.
It can also read all the engine codes as well as ABS (Anti Lock Brake System), SRS (Air-bag), and Transmission codes.
If you are looking for an OBD2 scan tool that can not only give emission pass or fail information but much more the INNOVA 6100P is worth a look.
OTOFIX D1 Lite Automotive OBD2 Scanner, [2 Years Free Update] 2023 with Bi-Directional Control Scan Tool, All System Diagnoses, 38+ Functions, Oil Reset, EPB, SAS, BMS, ABS Bleeding, Auto VIN, FCA SGW
While checking a vehicle’s emissions does not require a high-end scan tool, if you need one that does a lot more, the OTOFIX D1 Lite is a very nice option.
It is a Bi-directional scan tool, meaning it can not only read a vehicle computer but also send commands back.
Most will have no need for such an advanced scan tool, but if you are a busy DIY mechanic or a small shop, it is worth a look.
Knowing if a car or truck will pass an emission test before going to the testing station is a nice option to have.
A good OBDII scan tool can also show why a test will fail and what needs to be fixed.
Keep in mind that if there is a code on a vehicle and it is cleared, it will need to be driven for 20-30 miles to get what is called a drive cycle.
Smog testing stations can detect if a code has been recently deleted since the vehicle will not have enough data and need to be driven more.
There are many good units available, with those above some of our favorite options.
Do you have a favorite OBDII scan tool for an emission test? Let us know your thoughts below.