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Writer's pictureMark Ellison

Failed a smog check for incomplete OBD monitors? Now what?

Updated: Jan 3


So your vehicle failed an I/M inspection (smog check) for incomplete monitors and

you ask your technician, “how do I fix this?” The most used answer from your technician will generally be, “just drive the vehicle.” So, you drive your vehicle and the monitor still does not set to complete and your technician says, “drive it some more”. This is the definition of Insanity.


Well, I am here to tell you, you can drive your vehicle from California to Florida and then back to California, and the monitor still won’t set to complete. So now what? Heck, I’ll even go further with this…Your technician finally realizes there is a problem and you hire your technician to figure out this issue. This is a good thing since you did unnecessarily drive your vehicle at five bucks a gallon (thanks Joe) to get those monitors to set per the advice of your technician, all the while you figured out the expense of unnecessarily driving vehicle. Now, your technician states to you after spending a few hours on your vehicle, “there is nothing wrong with your vehicle.”


If this is you, than I certainly feel your pain and if you are the technician…well, read some more books.


On Board Diagnostic has been around for over 40 years. Federal regulation required vehicle manufactures to install an emissions monitoring system known as On Board Diagnostic Generation 2 or OBDII. OBDII was adapted in new passenger cars and light trucks in 1996.


An easy way I can explain the OBDII monitors is to know first what they are. Your vehicle has a computer in it we call a Powertrain Control Module or PCM for short. Inside of your PCM there is a service manager that has technicians employed to constantly check the emission controls and fuel feedback your vehicle has. The sole purpose of this is to check and verify your vehicle is running efficiently and not polluting our air. The service manager will assign a technician to check an emission control device such as the catalytic converter, air injection system, or an exhaust gas re-circulation system. The technician reports back to the service manager their findings. Now, to keep this simple…The technician will report back to the service manager a number from 1 thru 10. A number of 1 would represent the vehicle is brand new and still on the showroom floor and a number of 10 would represent a major problem with the vehicle and turn on the Check Engine Light (MIL). So, what if the PCM technician reports back an 8 to the service manager? An 8 would represent a problem causing the OBDII monitor to not set to completion, but not a bad enough of a problem to turn on the MIL.


Well, I'm here to help and I’m certainly not from the government.


You are the only one that really knows how your car runs since you drive it daily. So, ask yourself…How is my fuel mileage? How does my vehicle run today compared to yesterday? Do I hear noises that I have ignored by turning up the radio? If so, investigate those questions. If not, move onto what we call a Drive Cycle. Your vehicle manufacture publishes these drive cycles for each and every OBDII monitor. Most of the time you can find them on the internet. A Drive Cycle is the enabling criteria required to set monitors to complete. You must drive your vehicle a specific way the manufacture lays out. And, you must follow the drive cycle to a tee!


So, I would suggest you follow your vehicles manufacture drive cycle and perform these cycles at least twice. Once this is accomplished, check the I/M readiness monitors (OBDII monitors) with a scan tool to see if they did in fact complete. If they did complete, than awesome, and I hope you enjoyed your visit to Florida. Can you now see why I stated driving from California to Florida and back to California? More-than-likely while driving to Florida from California, the drive cycle was not performed or simply the service manger did not like what the technician was reporting.


Now, if the monitors did not complete after performing the drive cycle(s), you’re gonna have to find a technician that understands this problem. Not all technicians will either. Find a technician that knows about Mode 6. Mode 6 is the continuous monitoring of the non-continuous monitors as these are generally the monitor(s) you are having trouble with. This may sound confusing but it really isn’t. Search Mode 6 on the internet as you will be surprised on what you’ll find. Unfortunately, you will need an enhanced scan tool to gain access to Mode 6 and if you don’t have one, find a technician that does and knows Mode 6 to help you get through this troubling issue. Mode 6 will in fact aid you or your technician on why the monitor(s) will not set to complete. You will also need access to the vehicle manufactures Mode 6 information.


A dear friend of mine contacted me with an issue on the Heated Oxygen Sensor (HO2s) monitor not completing. Vehicle is registered in California and a smog check was coming do for registration. A vehicle in most all cases will not pass a California Smog Inspection with this monitor incomplete. I connected an enhanced scan tool to his vehicle and checked a few things out such as codes, parameter data, anything pending, and of course the monitors. I did not find anything out of the ordinary but did see in fact the vehicle HO2s heater monitor was incomplete. I next went into Mode 6 after locating Test Identification Data (TID) and Component Identification Data (CID) published by the vehicle manufacture. I did find Bank One Sensor One (B1S1) looked a bit wonky to me. I plugged in the Mode 6 data that was reporting on this sensor into the vehicle manufactures formula and discovered the sensor heater has higher than normal resistance creating a lower current flow through the heating element. This problem was not bad enough to turn on the Check Engine Light or set a code, but not good enough to set the monitor complete. My friend went to the dealer, bought a new sensor, installed it, and waited to the next morning to check the monitor since the monitor required a cold start to set. The monitor did indeed set right away. Now, many of you that may had this issue probably replaced all the sensors at an enormous cost. My friend’s vehicle has four oxygen sensors. Utilizing Mode 6 did pin point me directly to the problem saving the cost of replacing all four sensors and unnecessarily driving the vehicle at 5 Bucks, 6 Bucks, now up to 7 Bucks a gallon (thanks again Joe).



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