AKRON (June 9, 2003)—Onboard diagnostic systems such as OBD-II are more sophisticated and capable than ever before. But OBD-II may still cause untold confusion and anger when motorists fail to get straight answers about it from informed service writers and service managers.
Regular Tire Business readers know I have emphasized the need for informed service personnel for years. Although this doesn't mean that service managers and service writers need to become quasi-technicians, they do need to know certain things to serve their customers effectively. Selling OBD-II-related diagnosis and repairs is no exception.
The OBD-II diagnostic system appeared on the vast majority of vehicles sold in America in 1996. All too often, I see service personnel becoming exasperated with themselves and their customers because they can't explain some key points of this system.
I've seen countless cases where motorists return to a service shop complaining the check engine warning light on the dashboard has turned on. The vehicle may have come in re-cently because this light was on. When the customer left your service department, he or she thought you did fix the vehicle because the check engine light was off.
But other times, the check engine light was off when they brought the vehicle to you for maintenance or repairs. Several days pass by and suddenly the light's on for no obvious reason. It's also likely that there's no perceived performance problem, either. Some grossly simplified OBD-II information may save you a lot of arguments over that check engine light.
OBD-II doesn't wait for a catastrophic component failure somewhere to cause gross pollution—it watches for trends that suggest abnormal increases in tailpipe emissions. What's more, the OBD-II system is considerably more accurate because it's programmed to constantly evaluate itself.
In other words, the system constantly tests all its little subsystems to be sure everything's working correctly. Each one of these little subsystem self-tests is called a monitor. A technician can connect a tester (common OBD-II scanner) to the vehicle's underdash diagnostic connector and tell if the monitors already have run or are in the process of running.
By the way, one of the benefits of the OBD-II format was a largely standardized diagnostic connector.
An OBD-II scan tool can show a tech a display called “Readiness Status.” If the system has completed a given self-test or monitor, “completed” appears on the screen next to the name of the monitor. Remember that this system won't flag a problem, set a trouble code and light up the check engine light until the relevant monitor has been completed. For example, you really can't be sure if there's a potential EGR system code brewing until the engine control computer has completed or run the EGR monitor.
The bottom line: Your techs really can't be sure if any trouble codes are waiting in the wings until all the monitors have been completed. A customer may leave your dealership and happen to drive in just the right way to complete a particular monitor. Bingo! Through no fault of yours or your crew's, that darn check engine light is now illuminated!
The fun part of OBD-II is that it may take anywhere from 10 to 45 minutes to literally weeks to complete or run the vehicle's monitors. Time-wise, the smartest and most-practical approach may be to tell the motorist to drive the vehicle for days or weeks and then return for a quick “readiness status” checkup with the scan tool. Note that an OBD-II scan tool is the only way to check the monitors.
Fortunately, some aftermarket in-formation sources such as Motor publications and others offer guidebooks that explain how to drive a given OBD-II vehicle in order to complete certain monitors. For example, the guide may tell you that running a particular monitor requires starting the engine cold, warming it up and driving at 50-55 mph for several minutes. Finally, the guide may tell you to take your foot off the gas pedal so the vehicle abruptly decelerates from cruising speed down to idle speed. But completing some monitors isn't nearly this simple.
If your tech repairs a car and drives it long enough to complete all the monitors, the vehicle should be ready to go if no check engine light appears after the road test. But if the monitors aren't completed, you can't be sure there isn't a problem and a check engine light in the offing. Plan accordingly.