Auto Service World
Feature   June 1, 2006   by Jim Anderton, Technical Editor

OBD II and You

OBD II still causes many headaches. The right equipment eases the pain.

On-board diagnostics evolved in the early 90’s as a way for OEM’s to address the issues of emissions system complexity and the need to make smog-producing engines last long enough to meet U.S. federal regulations. With OBD came expensive diagnostic tools, equipment which has come down in price significantly over the past ten years.

Buying a scan tool? Today there are multiple low-cost options, allowing individual techs to purchase code readers with considerable sophistication. They’re often marketed as conforming to various Society of Automotive Engineers J-codes, codes which define how OBD-II operates. Standards are converging, but the aftermarket still has to repair millions of older OBD-II vehicles leaving their 10-year emissions durability window. Here are a few examples of the possible confusion when referring to SAE J-codes:


This is the SAE standard that makes all diagnostic plugs common.


The J1978 is the SAE’s standard for scan tools.


This is the SAE’s standard for test modes. Note that a scanner could be J1962-compliant, meaning that the cables fit into the vehicle’s diagnostic connector socket, but not strictly compliant with the scan tool standards J1978 or J1979. Read the literature carefully!

While OEM’s are moving toward standardization, if and when OBD-III arrives, technicians currently can face four common but different standards:

J1850 VPW

This is the SAE communication standard seen in GM vehicles.

J1850 PWM

Used on domestic Ford cars and light trucks.

ISO 9141

Not an SAE standard, but a communications mode set by the International Standards Organization and used by DaimlerChrysler and most imports.

What works with what?

Scan tools can retail for a hundred bucks or several thousand, so knowing how much capability the tool has and how much you need are essential. The U.S. Environmental Protection Agency has mandated standardized emission-related codes and many others are common. But there are also many proprietary or manufacturer-specific codes. Accessing these (where they’re not blocked) can speed diagnostics but come with a higher purchase price. Upgradeability is also an important consideration. Many low-cost code readers can’t be upgraded, while some high-end models can only be upgraded at high cost. How much do you need? If your shop specializes in imports, for example, buying extensive domestic vehicle coverage may not have a sensible payback. Can you buy just the coverage you need? Don’t overlook the cheaper units because they can’t be upgraded. It may be cheaper to simply throw the old unit away and start again, especially if your service tends toward straightforward repairs.

The essential feature

All big-time diagnostic tools have a “snapshot” or “freeze frame” feature that captures data for later replay. Low-cost handhelds may or may not have such a data capture feature, but consider making this feature mandatory for all tool purchases. Why? Many transient problems and drivability tests, as well as reprogramming tasks, require a road test. Can you have an accident while road testing a vehicle? Possibly, especially if you’re looking at a two-inch screen instead of on the road ahead while conducting that road test. Insurance companies haven’t figured this out yet, but they will. Better to capture the data and then do the analysis back at the shop.

What about warranties?

Scan tools are now an essential part of every tech’s daily routine, so downtime isn’t an option. A bad impact wrench, for example, may be returned for warranty work through your wagon Jobber who will often offer a loaner tool. If your bargain diagnostic tool quits, however, who honours the warranty on that tool? What do you do while its in the shop? For cheap handhelds, many techs simply buy another as they can make more money with zero downtime than they can waiting for the warranty fix. Ask other techs about reliability and warranty repair policies.

Central or distributed diagnostics?

If you’re planning a new shop, expanding or renovating an existing facility, you have several options for OBD II. The simplest model is to rely on techs supplying their own equipment. The second option, has the shop owning the expensive multi-feature tool, while techs optionally purchase simpler personal scan tools. The “Cadillac” strategy is to use an integrated shop-wide system (like the Delphi DS-series) and run it in combination with shop management and parts ordering software. There are advantages and disadvantages to all three. The cheapest and simplest solution is “every-tech-for him/herself,” but that means no commonality amongst bays, so one solution isn’t easily shared among techs. Training is zero-cost, since it’s the tech’s personal tool, but how do you upgrade either the tool or the tech business-wide? Where the business owns an expensive tool, the shop purchases its training, while individual techs use cheap handhelds with little or no training as a rough test. The integrated option is major money, but it’s also the most productive, as well as allowing common training for the entire technician staff.

As a built-in fixture like a lift or alignment rack, integrated systems also require training which is less portable than that for personal tools, which may be an advantage or a disadvantage, depending on whether you’re an owner or a technician employee.

What about OBD III?

The third generation of on-board diagnostics has been discussed for over ten years and while there’s no clear consensus about what form it will take, look to the U.S. federal government, or possibly the state of California, to take the lead. Several proposals suggest a system like OBD II, but with a remote monitoring capability that would allow roadside scanners to alert police or environmental officials that a code has been set. Presumably, a ticket would be issued, or a summons to repair the vehicle within a short time. Other proposals include code reporting automatically, using cellular phone technology or satellites, allowing vehicle licensing officials to mail repair notices directly to vehicle owners. While proposals like these could boost service business, some OEMs systems like OnStar already have remote sensing capability. If OEM’s can convince regulators to use the systems to notify owners, dealer service departments will have a built-in advantage. On the other hand, service businesses with a regular clientele might be able to use the technology to notify owners that they need service immediately. It’s another “right-to-repair” issue that will have to be fought on Parliament Hill, before it impacts independent service operations negatively.

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