DETROIT-New On-Board Diagnostics II testers-or hand-held ``scan tools''-are cheaper, easier alternatives to diagnosing sick cars that make it easier for technicians to check the health of a variety of cars and light-duty trucks. Many tool makers already offer these hand-held test meters to access a vehicle's on-board computer. Prices range from $500 to $3,000. They're not exactly cheap, but these tools offer high levels of capability relative to $50,000 PC-based, roll-away diagnostic units.
Scan tools were originally intended to do quick computer and sensor-function checks on the assembly line. At first, each maker had its own plug-in terminal and tool. Eventually, makers and federal and state regulators realized that technician access to the on-board computer with a hand tool would enhance field service. Cars running correctly pollute less.
Starting in 1989, the California Air Resources Board (CARB) wrote laws requiring passenger cars to have on-board diagnostic systems by 1994. On-board computers have replaced many mechanical components with electronic sensors and electrically controlled actuators. These can be monitored and controlled by a scan tool tapped into the computer's diagnostic plug and software.
Vehicle computers automatically monitor sensor health and will store ``trouble codes'' that point to dead or dying components or sensors. Some 1995 General Motors vehicles will set over 150 codes.
New-car dealerships bought scan tools common to their brands. But private garages, which handled a wider variety of models, had to make large investments in different scan tools.
Some manufacturers, such as Snap-On Tools Corp., eventually offered one tool with a variety of plug adapters and brand-specific computer diagnostic cartridges. Another firm, Mac Tools Inc., makes the Mastertech scan tool, featuring a built-in lab scope to help catch intermittent gremlins.
Robert Bosch Corp. offers KTS 300, which talks to many import cars with Bosch's Motronic engine management system.
Recent on-board diagnostics legislation is intended to commonize a vehicle's diagnostic plug, its location, the terminal assignments and the meter.
On-Board Diagnostics II was mandated by CARB for adoption by automakers during the 1994 to 1996 phase-in period. The Environmental Protection Agency and state agencies are adopting similar standards. State and federal governments want to make sure cars, particularly those that pollute too much, get fixed cheaply and easily.
``The problem is that many of the emissions systems, particularly the catalytic converter, can fail without having any symptoms the customer can perceive,'' said Susan Christophersen, a senior program developer with GM's Service Technology Group.
OBD II affects vehicle service in four areas:
Vehicle interface protocols;
Standardized vehicle to monitor connectors;
Diagnostic requirements; and
Standardized language to describe devices and problems.
So far, the service reality is not meeting the service ideal. Several significant kinks need to be ironed out before all service centers can speak any car's language.
For example, many carmakers reported late last year that they had problems with more sophisticated OBD II diagnostics. These systems light the instrument panel's ``malfunction indicator light'' to show when emissions exceed a specified emission rate or the engine misfires a cylinder.
But the light was initially coming on when the vehicle accelerated hard on rough roads. Apparent-ly, a sensor was reading crank-shaft speed fluctuations caused by the rough roads as a misfire. And that was storing a trouble code that would be read by the scan tool as a misfire. So scan tools aren't always a sure-fire cure.
Ray Corbin, program manager for V-6 development at GM's Powertrain Division, said Corvette and compact truck models that were pilots for OBD II's more complex diagnostics are working well now.
``We're confident today that when a malfunction light is lit, there really is something wrong,'' he said. ``In the very beginning, we were not always sure. And we disliked warning customers with the light if nothing was wrong.''
An obvious problem is carmaker resistance to providing in-depth service information to the private service industry, even while meeting the letter of the law.
Carmakers have resisted giving out detailed emissions-service data they've spent years and millions of dollars to create and refine. They also don't want to provide computer recalibration access to the private service industry.
The makers argue that unauthorized tampering could cause early failure of emissions components-expensive parts that makers could be liable for covering due to 10-year/100,000-mile federally mandated warranties.
The private sector counters that without reasonable access it would be unable to make emissions-related tweaks and would be locked out of that service business.
Still, carmakers and service tool suppliers are on their way to making one scan tool for all vehicles.