Auto Service World
Feature   September 1, 2008   by Jim Anderton, Technical Editor

The OBD Dilemma

OBD-II makes diagnosis for accurate repair much easier ... but also makes the need for better computer skills and training more pressing

A dozen years into the OBD-II age, with vehicles lasting longer and the Canadian economy flirting with recession, this is a Golden Age for on-board diagnostics. With relatively few vehicles left in the active fleet that are pre-OBD, the scan tool has had half a generation to become arguably the most important tool in any technician’s box. It’s been here a while, it works, but it’s also often underused and sometimes misunderstood by technicians who use it day in and day out.

Making sense of OBD-II, and more importantly, making money with it follows the familiar pattern for our industry: the right combination of good people using good tools. Darryl Scott, division supervisor for Versatile Automotive Diagnostics, notes the Canadian aftermarket is at the cusp of full acceptance of the need for wider and deeper OBD coverage.

“They’re just beginning to recognize it. As the more sophisticated vehicles are coming off warranty, they need to be ready. Independent garages are very budget conscious; they don’t want to spend $3,000 on a factory scan tool, but they want to be able to service a wide range of vehicles.” According to Scott, the challenge to shop owner and technician alike is simple: “It’s constantly changing. New failure codes are emerging all the time, and new connection speeds as well.”

Are the technicians keeping up? “I think they are. They recognize the need to keep up with the technology to be able to service the wide range of vehicles today,” he adds.

The tools are more complex with greater functionality with each generation, but are the technical knowledge base in the individual tech’s head enough?

Bosch Diagnostics’ Canadian business manager Patrick Dubois is positive: “The better trained techs get it right away. Most want to just skim the surface of what the product can do, from a features and benefits standpoint; they want a tool to turn off the “check engine” light. There’s a lot of functionality they’re missing.”

Dubois notes the push to faster throughput in the bays is a factor. “It’s definitely a part of it. The way the flat rate model works for example, means they often just don’t have the time for a proper diagnosis. The compensation system is a serious issue.”

Want to stay ahead? Keep up with new computer technology

What’s Dubois’ most important issue going forward for OBD-based diagnosis for the average tech? “Get your computer skills up! Most equipment is going PC-based, so it will be essential for the future,” he says emphatically.

Dubois notes that most diagnostic tools will use Windows-based platforms for the foreseeable future, but emphasis-es that no computer training is wasted. It’s possible to spend as little as $200 or less for a code reader, to tens-of-thousands for integrated wireless tablet PC system. How much is the right amount for a given shop? According to John Mills, national technical trainer for SPX Service Solutions, the key is to accurately determine what the business intends to do in diagnostics, then buy equipment to meet that need.

“Lower cost units are simply OBDII code readers, while more sophisticated tools add late OBD-II features like CAN (Controller Area Network). Moving up in sophistication, better equipment adds bi-directional testing, repair data and diagrams,” he continues.

Mills notes shops specializing in a only a few makes may benefit from OEM-type diagnostic tools, but that’s rarely the case in most Canadian repair businesses: “A very knowledgeable technician, specializing in only a few vehicle models, might get by with just a scan tool, but there’s no such thing as a ‘one size fits all’ solution.”

One dish, several flavours

OBD, while a rare success in industry standardization compared to the mainstream computer industry, isn’t truly universal. Although the command set is locked into the SAE (Society of Automotive Engineers) J1979 standard, there are three variations of OBD-II that vary the way a scan tool communicates with the vehicle. General Motors vehicles use a system that varies the pulse width (SAE J1850), while Ford uses a non-variable pulse width data stream under SAE J1850. Chrysler, most Asian and European vehicles use a non-SAE standard called ISO 9141. And the systems are evolving all the time, making it impossible to create a one-size-fits-all scan tool that doesn’t require updates.

According to the public-service OBD website,if a vehicle isn’t pre-programmed into a technician’s system, the configuration of the data link connector gives a clue. A pin in the #7 position but none at the #2 or #10 slot means ISO 9141. If there’s no pin at #7, the vehicle uses an SAE protocol, but no pins in #7, #2 and/ or #10 mean a vehicle that may use the ISO protocol.

The upshot of this techno-speak is that it’s important to know which system you’re working with, which means diagnostic tools that ideally do the thinking for the tech through clear, menu-driven user interfaces that ideally reference individual makes and models. A Cadillac Catera, for example, is essentially an Opel, making it more similar to European cars than a DeVille, at least diagnostically. Simple menu-driven commands keep confusion at a minimum, especially as manufacturers source vehicles built in factories across the globe.

While there are various flavours of OBD-II systems, from a technician’s point-of-view the important parts are what the OBD-II system is measuring and what the outputs mean. A typical system will monitor up to 11 emissions/ drivability-related parameters, but only the drivability component set (MAP, MAF, TPS etc.), misfire and fuel trim are monitored continuously. Converters, evap leak O2 sensor (with its heater) EGR and sometimes A/C cycle and secondary air injection are monitored, but are sampled periodically, by a routine unique to the vehicle manufacturer. Similarly, the number of failures detected before the MIL is set can vary (although two is a common trip point) resulting in similar drivability or emissions issues which show up differently on different vehicle brands. For an all-makes shop, this limits the ability of most technicians to use past experience as a guide to a speedy and effective repair, forcing all techs to spend more time and care interpreting scan tool results.

Unfortunately, motorists can’t help the process, often because the evap leak test will frequently set the MIL for a loose gas cap, which many consumers won’t stop to correct. The result is a continuous “Check Engine” warning which is ignored by vehicle owners until the problem affects drivability, seriously degrades economy or causes a Drive Clean or AirCare failure. While manufacturers are only required to set the MIL to light for emission-related failures, consumer perception is that the MIL lights up frequently and spuriously, a perception that’s reinforced by ECM “limp-home” modes that can map fuel trim accurately enough, even with damaged sensors, that drivability is hardly affected from the driver’s perspective. Add the tendency of older off-warranty vehicles to have noisier cabins due to suspension component wear, cheap replacement tires and damaged exhaust systems and the result is a fleet with poor performance and dirty emissions, with an owner that doesn’t know the difference.

Are you ready?

While the self-diagnostic capability of OBD-II systems makes common failures much easier to troubleshoot, completing the service means resetting the system. Power interruption to the vehicle’s ECU, and in many vehicles, disconnecting the battery terminals requires a scan for readiness monitors. Modern scan tools detect and report readiness codes for each scanned component, but with the increase in the number of subsystems that are now have DTC’s, it’s not as simple as clearing codes and looking for the “ready” flag from the tool’s screen. A thorough reset on a modern vehicle requires a road test, at minimum a brief drive to loa
d the engine, cycle transmission solenoids and bring the engine to true operating temperature. Note that checking the readiness monitor is still a valid and billable service procedure even if no codes are set in cases where the battery was disconnected or ECU power cut for other electrical work. Low-end body shops routinely miss this procedure, so if a regular customer has had a recent body repair; it’s worth a quick look.


The next generation of on-board diagnostics is in a sense, already here with GM’s OnStar system. Wireless connectivity is the future, with vehicles reporting trouble codes and higher level diagnostic information, like driving patterns and kilometres logged, to either dedicated diagnostic tools or increasingly, palm PCs and other general purpose computers with diagnostic software. OEMs are already using this technology to flag owners to problems and of course, book an appointment with their dealer for service. Without an aftermarket network like OnStar, the ability to compete with OEM technology in diagnostic marketing to consumers will have to wait until low cost Web transceivers are available that will interface with the vehicle diagnostics, then E-mail trouble codes to independent service centres. If future protocols are open-source, the way California Air Resources Board regulations wedged OBD-II open to the aftermarket, it may be possible to perform “drive-by scanning,” pulling codes as vehicles enter for fuel, convenience purchases or simply drive across the lot. The marketing advantage is obvious; if an owner can be approached for a “while-you- wait” hard scan after the wireless notification, passing motorists can become regular customers.

While this level of technology is still in the future, the fact is that OBD-II is not only working, it’s working well enough to challenge the dynamometer as an I/M inspection tool, a possibility not welcomed in Ontario, where Drive Clean shops have considerable investments in rolling-road dynos and test equipment. OBD-II is also a driver for higher vehicle quality.

According to a 2002 report by the US Federal Clean Air Act Advisory Committee, in 2001 approximately 961 thousand vehicles were recalled, of which 74 per cent were attributed to OBD-II’s diagnostic capability. Only 23 per cent were non-OBD related recalls, and the remaining three per cent were OEM software problems. “They all run like that” isn’t a valid conclusion anymore with OBD systems watching.

Can you make money with OBDII? To survive, shops have little choice, but the ability to use it to add perceived value to customer service (“We’ve scanned your car and everything is O. K.”) and lock in the critical customer-service writer relationship is still underdeveloped. As OEM dealers use national advertising to promote high-tech service capability, the need for independents to fight back with capable diagnostic technology of their own isn’t an option, but a priority for survival.



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