Instructables

How To Pass Inspection & Complete A Drive Cycle

video How To Pass Inspection & Complete A Drive Cycle
In this video I'll show you how to complete a drive cycle and pass inspection after turing off your check engine light.  It is true that your car will not pass inspection if the check engine light is on.  However there is more to it than simply turning it off.  By the way the easiest way to turn off the check engine light would be to disconnect the battery for 30 seconds.  Inorder to pass inspection your car needs to complete a full drive cycle so that all (8) internal monitors have a status of "Ready".  If any of the (8) monitors have a status of "Incomplete" that means you have not yet completed a full drive cycle and you need to drive your car around more.  Your car will need to experience city driving situations and highway driving situations inorder to complete a full drive cycle.  

Usually if your check engine light is on that means you need some repair work done on your car but that is not always the case.  I drive a 2002 Chevy Impala and the check engine light has been coming on for about 4 years.  The trouble code is "P0420".  That means the catalytic converter is functioning below the normal efficiency levels.  Back in 2007 when I first noticed the problem I had the catalytic converter replaced.  At that time the performance of the Impala was greatly reduced.  Specifically when ever the accelerator was pressed there was a significant time delay before the car would accelerate.  It almost seemed as if the transmission was slipping and then suddenly it would catch and the car would accelerate.  The problem however was not the automatic transmission.  The problem was the catalytic converter.  There was a carbon blockage that clogged the air flowing through the power train.  Exhaust was escaping through the EGR valve because the catalytic convert was blocked up so much.  So I bought the new catalytic converter.  The cost was roughly $800 as I learned that my vehicle was manufactured to the California emissions standards and not the federal emissions standars.  That was news to me.

About two or three months after the catalytic convert was replaced the check engine light came on again.  This is around the time I asked for an OBD-II code scanner for Christmas.  The same "P0240" trouble code was being stored in the engine control module.  The catalytic converter was under warranty so I had it replaced thinking it may have been defective.  Again the "P0420" trouble code came back.  At this point I started to see a pattern.

There was no performance problem with my car anymore.  That had been resolved after the first catalytic converter was installed.  The only issue was that the check engine light kept coming on.  The Oxygen Sensors before and after the catalytic convert have been tested and I was assured they were functioning properly.  If the Oxygen Sensors are out of whack that could possibly trick the engine control module into thinking that there is a problem with the catalytic converter.  So that was ruled out.  

To this day in order to pass inspection I have to erase the check engine light and complete a drive cycle.  Only then will my car pass inspection.  Of course two weeks after the inspection the check engine light will come back on.  Hope this informations helps someone out, or maybe you have your own theory about whats really wrong.  I would love to hear your thoughts.

BigNate84 How To Videos
HuanN17 days ago

Extremely helpful. I have a Honda Accord 2001. Its original Cat was broken last year. I replaced it with a new after-market one from Midas. But after a while the check-engine light came back due to that P0420 code. Midas then changed the Oxygen sensor, but that did not help. They then replaced the Cat with another one of better quality (and I had to pay more), but it did not solve the problem either. I brought the car back to them a few times more, and they could not get rid of the code permanently. I got tired and did not bring the car back to Midas for warrantee any more. But the deadline come for me to have the emission test done. So I disconnected the battery to get rid of the check-engine light just before brought the care in for an emission test. It failed because the car was not ready as you explained. So I disconnected the battery again and followed suggested procedures to get the car ready for a test (while making sure I brought it in for a test before driving it too long and causing the check-egine light to come back). If passed! If I had learned about your experience, I would not have lost so much time and money (bringing the car back to Midas many times and paid extra money). But thank you so much for sharing this very helpful information.

ChristopherW2 months ago

Wow... just wow... My car is a 2003 Toyota Corolla, but reading your story really made me think you were driving the same car I was/am. I've been having problems with the Cat for years, and have had quite a bit of work done in order to pass inspection. Still though, that blasted light refuses to stay dead for long, and it's always the same, lousy "P0240" trouble code. Mine was also apparently manufactured to the California emissions standards, and so on and so forth.

Thank you so much for sharing your experiences and knowledge here.

What is the drive cycle for a 2003 Pontiac Bonneville?? I can't find it and I don't have one of the gadgets to check
rannadurai2 years ago
I have the same exact problem too. I heard from my mechanic that unless we use a OEM Cat from the Dealer, the dreaded P0420 keeps coming back. No matter how many after market Cats tried upon.

These O2 Sensors are so tricky that they are almost fool proof.

However, I have also seen people trying the O2 Spacers (Like a 1-2 inch steel tube for the O2 sensor, that spaces out the sensor from the Cat's air flow). This tricks the vehicle's ECM to think that the CAT is still working under normal effeciency.

I have also read people using the "DIODE TRICK" where a diode is connected in series to O2 sensors signal cable to drop the signal voltage., again making the ECU think that the CAT is normal.

Personally for me the Diode trick did not work. As the ECU throws a new Error code (and CEL) for Resistance Too High on the sensor.
Davidbnner2 years ago
Hey Nate I have the same car. The problem is in fact your Catalytic converter. I have been going through the same process Hear in Texas for the last four years. Five cats later. I finally bought one from Eastern converters online. It was made especially for the impala. So far it works, but the tranny blew so I have not driven the care in a while.
BigNate84 (author)  Davidbnner2 years ago
Thanks for the feedback David. Its good to know I'm not the only one! My dad is convinced its a manufacturing problem with the catalytic converters. He was so curious he actually sawed the thing in half and inspected the honey comb filter inside the cat. It was pretty obvious that some of the material inside the cat wasn't in the correct place, and hence impeding the air flow. Let me know know if the Eastern converts cat works out after you put some miles on it. Maybe I'll pick one up. Thanks again.