The PCM or powertrain control module of a vehicle uses a certain method as drive cycle to find out if an emissions system repair is successfully done. This method involves a special test drive as if driving to work by duplicating the scenario of the driver from starting a car and going for a short trip on a freeway. A series of tests by the engine computer runs to see if the emissions system is properly working.
Drive Cycle and its purpose
The PCM or powertrain control module records the fault code and emission system problem signaled by the Service Engine Soon Light or the Check Engine. The Service Engine Soon Light or the Check Engine is triggered when the emission system has a problem. The indicated problem by the fault code must be diagnosed and repaired accurately.
There will be a series of tests following the repair, fault code cleared, to find out if the repair effectively fixed the problem and if the emissions systems are properly running. You’ll know they do when they the emissions released in the atmosphere from the vehicle are minimized. The design of this process was made to keep the vehicle from slipping through with a problem in an emissions test. The Emissions Readiness Monitors and Drive Cycle have mostly stopped an unethical tactic used until 1996 where the Check Engine Light is turned off by clearing the code prior to the emissions test.
The Basic Drive Cycle, Performed!
How do you do the basic Drive cycle? Here are step-by-step guidelines that are effective to complete the readiness monitors for the emissions control system of your vehicle.
First step: Getting your vehicle prepared
Have your tank filled, not completely full and avoid having your fuel tank nearly empty or most of the test will not run.. Have it around 30% to 70% full. Some systems need to have a specific fuel level, just like the EVAP system.
You need a strong battery and a good alternator to keep you from jump-starting. This would mean that your PCM or powertrain control module is erased along with data tracking the results from the Drive Cycle Stages. Some tests won’t run with an undercharged or a weak battery.
Make sure that your vehicle would rest in an environment that’s less than 90 degrees Fahrenheit or at least let it sit for 8 hours.To establish an accurate baseline for the test, the air temperature needs to match the outside temperature. The EVAP system won’t even run if the fuel gets too volatile due to the outside temperature that is over 90 degrees Fahrenheit.
Make sure to close the doors and leave the keys out of the ignition when you leave your vehicle to sit all night. Onboard computers may ‘boot up’ when keys are in the ignition. Even the computers could still run until the doors of your vehicle are closed. Both have to be checked before leaving the vehicle.
Second step: Cold start
Here, you need to start your vehicle and let it stay in Park or Neutral, idle for around two to three minutes. While your vehicle idles, turn your headlights ON along with the defroster/heater, and the rear defroster from three to five minutes as a warm-up. The idle speed should be left alone until it gets to the normal speed.
Put your vehicle in gear, driving it through the city with a speed of around 25 mph. Let it go up to 35-40 mph a few times before you slow down and make a full stop. Don’t roll, you really have to stop the car just like what was taught in the driving school. Normally accelerate in every stop you make without being too fast or too slow.
Third step: Short Trip on the Freeway
Now that you’re done having your vehicle cold start and a few miles drive in the streets, take it out for a short freeway trip. Enter on-ramp when you’re the freeway, giving enough room with enough space from other vehicles allowing you to do a ½ to ⅓ throttle acceleration to the speed of the freeway.
Upon 60 mph acceleration, merge into the traffic safely. Make sure that you stay in the slow lane. You should maintain speed around 55-60 mph in the slow lane in 5 miles minimum. It would be advisable to maintain your speed by using the cruise control.
You must find a nice ramp that’s long enough to exit the freeway. While exiting your foot should be off of the accelerator, letting the vehicle coast down until it stops under its power while exiting completely from the freeway. Do not shift gears and don’t use the foot brake either until you reach the very end of this phase.
Fourth step: More driving in the city
now, you have completed the trip on the freeway. It’s time to drive through the streets in the city and repeat what you did in the second part of the Second step.
You should go up to around 35 to 40 mph for a few times and maintain the city speed of 25 mph prior to slowing to a stop. Like the previous stops you’ve been making, don’t toll through the stop and normally accelerate your vehicle.
Pull into your choice of parking space and let the engine idle for around two to three minutes before you shut it off.
Fifth step: Readiness Monitors, checked and verified
Go to a local auto shop and have them re-check your readiness monitors, pending codes, and present codes. This is done for free as a courtesy.
If there are no pending codes and your monitors are ready, your vehicle is repaired properly, ready for a normal drive and an emissions inspection.
How did your basic drive cycle go? Want to see it video? Check out this amazing video where as the vehicle monitors are set under 10 miles.