OBD II Drive Cycles
Posted by Alex (Im) E. on 01 February 2013 12:48 AM
OBD II DRIVE CYCLES
For a system that is supposed to be standardized OBD II drive cycles are not. For what ever reason, each vehicle manufacturer came up with their own unique drive cycles that must be followed before certain OBD II monitors will run their self checks.
The toughest monitors to set are the catalyst monitor and the EVAP monitor because these two monitors typically require the most complicated drive cycles.
Because there are so many different makes and model of vehicles, we cannot include all of the individual drive cycles in this reference program.
For vehicle specific details, you should consult the OEM service literature or applicable technical service bulletins.
Many drive traces have "prerequisites" (conditions that must exist) before they will run or set a diagnostic trouble code.
The ambient temperature may have to be above a certain degree, or the vehicle may have had to sit for a certain period of time since it was last driven.
For example, some vehicle manufacturers require an eight hour cold soak period before it will run the EVAP monitor.
The PCM has a timer that keeps track of how long the vehicle has sit since it was last driven.
If it hasn't been a full eight hours, the EVAP monitor won't run until the required time period has passed.
Test driving a vehicle in an attempt to get all the monitors to run is best done with two people: one to drive and one to check the readiness status on a scan tool.
Don't try to drive and read a scan tool at the same time or you may find yourself making an unplanned trip to an emergency room.
As a rule, driving on flat terrain will set the monitors more quickly than driving on hilly terrain.
You should also accelerate gradually rather than flooring the throttle, and brake smoothly (don't slam on the brakes).
Aggressive driving won't speed up the process and may actually delay the setting of some monitors. It takes time so be patient.
If you are having problems getting a monitor to run, remember that some monitors are load sensitive.
Shifting to a lower gear or disengaging overdrive may reduce the load just enough so the monitor will run.
Extreme ambient temperatures (100 degrees F or higher) may also inhibit some monitors from running. Your only option here is wait until the weather cools to run your drive cycle.
If a front-wheel drive or rear-wheel drive vehicle is being run on a dyno or road simulator, follow all the usual safety precautions such as making sure the vehicle is properly tethered or chained down, the parking brake is set (front-wheel drive only), the non-drive wheels are chocked, and no one is standing in front of the vehicle.
A floor fan may also be required to help cool the radiator for sustained high speed operation.
UNIVERSAL DRIVE CYCLE
There's really no such thing as a universal drive trace that works for all vehicles, but this one may work if you don't have the official OEM drive cycle:
Check if your car manufacturer is included in our Drive Cycle database.