Auto Service World
Feature   July 1, 2004   by Jim Anderton

OBD II For the Road

As on-board diagnostics matures with OBD II, are techs finding it easier to pick the computers' electronic brains?

It’s the summer of 2004, and for shops across the country, this may be a pivotal year. Why? The demographic bulge of OBD II equipped vehicles is now old enough to form the vast majority of many shops’ volume. OBD II promised the aftermarket a much easier diagnostic task compared to manufacturer-specific trouble codes and with modern scan tools and training, the transition has been relatively smooth for advanced shops. The computer, ECM, ECU, PCM, (or one of many other names, many unprintable), however, still gets much of the blame for system faults.

Has OBD II made life easier?

“A little bit”, states North Vancouver O.K Tire technician Dave Daley, adding, “It’s definitely a lot more informative as far as the OBD I system was because it’s fairly generic. The only downside, even with the latest software, is you often can’t get into the manufacturer’s protocol. For a specific manufacturer it’s often not too informative.”

Daley notes that reflashing ECU’s isn’t an in-house task, but there are some alternatives: “For reflashes on computers you have to either take it to the dealer because they have the software to diagnose whether it’s a problem with the computer, or just the software that’s loaded onto it. So either we’ll take it to the dealer or suggest that the client take it down and have them go through it. Especially General Motors reflashes, Standard Blue Streak have made it available to us. We can actually take the computer out, send it into a depot fairly close to here and have the information scrubbed and the new information loaded up. They’re charging on average $170 to do that. But with Dodge and Ford that’s not available to us at all.”

South of the border, right-to-repair legislation may open up proprietary software to independents, but the issue isn’t before Parliament, and OEM’s have the capability to block access from Canada, so for now, dealers have an advantage.

Does this make OBD II ineffective? Not according to John Cabral, technical manager for Blue Streak Electronics. “It’s a little more complete than OBD I and I don’t think the techs have fully grasped it yet”, he relates. “The most important thing is to have the right tools. You need a good scan tool with full coverage. They need to mimic the way the OE’s think, and display the right trouble codes. That way they can consult Mitchell, Alldata or the factory service manuals and solve it through the “tree”. If they do that you can pretty much guarantee a successful fix.”

David A. Dueck, technician at Lethbridge Alberta based Mo-Tire Auto Centre, agrees. “Compared to OBD I you have a lot more information in there as far as what’s going on with the vehicle. Before you could look at 20-30 different things going on with the sensors, now there are 30-70 different things you could be looking at. But that just assists us in diagnosing us with the problems. It’s pretty comprehensive.”

What do you do, however, when you’re troubleshooting “by the book” and you come across the dreaded “replace with known good unit’?

According to Jeff Elder, marketing Manager, Blue Streak Electronics, “in that case the aftermarket technician sometimes has to order one in and buy it, then if it doesn’t solve the problem, return it. The market place being what it is, you can’t return electrical parts so it comes back as warranty. It’s been an issue for electrical parts forever, but it’s a bigger problem for ECM’s because they’re difficult to diagnose. Warranty rates are relatively constant between OBD I and OBD II.”

Generating spurious warranty returns isn’t a ticket to profitability, but fortunately much of what fails inside the box is often about getting the data into and out of it through its connectors. Keeping the units corrosion and dirt-free is important, but the OEM’s often complicate matters. John Cabral relates:

“It’s often not the tech’s themselves. Sometimes the manufacturers design these things with the ECM’s in unbelievable places. There are late-model GMC Savannas, for example, with the module on the wheel well. Even though it’s sealed, if you put it through some harsh Canadian winters, it won’t last as long. The Suzuki Sidekick is another example.”

Contact enhancing chemicals are available for critical current paths like data connectors. Cabral states, “In cases where you already have some corrosion on the contacts it’s a good idea to use it. We’ve had cases where we get an ECU back and we can’t find anything wrong with it. On further investigation with the tech, we find that the original one was corroded. The frequent fix is to clean out the connector.”

Like many computer technologies that inside the “chip” are impossible to troubleshoot, computers take a disproportionate amount of the blame when systems fail. As Blue Streak’s Cabral says, “That’s always been the case. There are a few techs that use computers as a diagnostic tool. It happens, mostly with techs that are not as well trained, but it’s getting better as time progresses.”

Training is a given for shops that expect to survive the next decade, but there’s no magic formula for the type or amount that’s needed to create and maintain troubleshooting proficiency.

Dave Daley has no fears about the speed or change in control electronics: “God no! I train 2 or 3 times a month. You’re not in the business unless you’re in training these days. If you don’t, you just fall by the wayside. I train with 18 to 20 people at a time. Some of the courses are pretty pricey, but they’re worth their weight in gold.” Daley trains with Injectronics.

In Lethbridge, Dave Dueck notes that late model technology is especially difficult to assimilate until the aftermarket training resources respond. “2003 or 2004 product, you can’t keep up with that. It happens too quickly. For vehicles older than that, there are companies that give us training clinics. I go once or twice a year. To keep up with what’s going on, I think that’s enough.”

Mo-Tire and Auto Center manager Brian Roelofs takes advantage of training clinics that are sponsored by suppliers such as AC Delco, sending techs 3 or 4 times per year.

There is no magic bullet or secret strategy that can make difficult computer diagnostic work easy. Regular training, good tools and the regular application of common sense help here as in any other automotive repair task. Fortunately with OBD II, you don’t have to know what’s inside the ECU box to work up a decision tree that will usually lead to the fastest fix with the least frustration. That’s what profitable service is all about.


For all the control electronics that complicate modern vehicles, the mechanisms that do the “heavy lifting” in most automotive systems are straight out of the 1930’s. Braking, for example, still depends on simple hydraulics, while hydraulic power steering is only now being challenged by electro-magnetic assist technology.

According to SKF Linear Motion and Precision Technologies Canada’s Jennifer Sachs, electrical actuators may be ready to usurp mechanical drives throughout the chassis and engine. According to Sachs, “The industry where it is most evident is aerospace, where the fly-by-wire concept has meant a replacement of many of the hydraulic systems with electromechanical actuators. Similarly in the automotive industry, hydraulic brake, clutch, and steering systems may well be substituted by the electromechanical actuators of “drive-by-wire” technology.”

The relatively small forces required by the throttle control actuator, for example, are little more than those already used for EGR valve and ISC motor systems in use for years. The real breakthrough will require electromechanical actuators that can apply the serious forces needed for components like brake calipers or clutch packs. Sachs notes that power is no longer a limiting factor in automotive actuator design: “Engineers often believed that electromechanical linear systems could substitute hydraulic systems only in the low load range. This is no longer the case, a perfect example being the “E-Truck”, a fully electric concept fork-lift truck with a lifting force of 3.5 tonnes, presented by SKF at a recent Hannover Fair in Germany. Even in plastic injection moulding, where very large injection, ejection and clamping processes were generally actuated hydraulically, now all-electric machines are continually gaining market share.”

“Dry” brake systems and automatic transmissions? The technology is in place and they could be considerably cheaper to build, as well as generating significant fuel savings, since electromechanical devices convert electrical power into motion with minimal heat or frictional power losses. It won’t happen overnight, but as 42-volt electrical architecture gains ground in automotive design, OEM’s are sure to be tempted by all-electric actuation.


Sensors form a large part of suspected ECU failures, and they go by many terms, official and slang. Here’s a list of correct terms, courtesy of Delphi Product & Service Solutions:

Air Charge Temperature Sensor:

Reads air/fuel mixture temperature and relays a voltage signal to the computer, which uses input to adjust the air/fuel ratio.

Air Cleaner Temperature Sensor:

Calibrated to open and close vacuum actuator when specified temperatures are reached.

Airflow Meter/Sensor:

Measures the amount of air coming into the engine, while compensating for altitude (density) and temperature differences and sends voltage signal to computer, which uses input to determine proper air/fuel mixture.

Air Temperature Sensor:

Used on Chrysler TBI systems. It signals the computer with the temperature of the air in the throttle body assembly during hot restarts.

Ambient Air Temperature Sensor:

Reads outside temperature

Camshaft or Crankshaft Position Sensor:

Electrical device that measures position of crankshaft for triggering ignition or fuel injection system at a proper time.

Coolant Temperature Sensor:

Detects the coolant temperature and sends this information to the computer. The computer can then control several aspects of engine performance, such as fuel mixture, spark advance and cold start idle.

Coolant Temperature Gauge Sensor:

Sometimes known as temperature sending unit, this sensor also measures the coolant temperature. It sends this information to the temperature gauge or light rather than the computer.

EGR Valve Position Sensor:

Monitors EGR valve stem and sends voltage signal of its position to the computer, which uses input to regulate the amount of exhaust gas passing through the EGR valve.

Intake Air Temperature Sensor:

This sensor, used on EFI models, provides the computer with air/fuel mixture temperature information. It is used both as a density corrector to airflow calculation and to proportion the cold enrichment fuel flow. The sensor is mounted in the intake manifold or on the air cleaner and is also referred to as air charge temperature sensor, air cleaner air temperature sensor, charge/ engine temperature sensor and manifold air temperature sensor.

Knock (Detonation) Sensor:

Sends voltage signals to the computer, which uses input to retard spark timing when engine pings.

Manifold Air Temperature Sensor:

Refer to intake air temperature sensor.

MAP Sensor:

Reads change in manifold pressure (vacuum) and sends voltage signal to the computer which uses various adjustments such as air/fuel ratio, spark advance and torque converter clutch.

Mass Airflow Sensor (MAF):

See airflow meter/sensor.

Speed Sensor:

Sends vehicle speed information to the computer. It can be found on the transmission or gauge cluster.

Throttle Position Sensor (TPS):

Senses throttle movement and change of position and supplies an electrical signal to the computer. These signals then inform the computer to regulate various engine and vehicle operations, such as spark timing, air/fuel ratio, torque converter lockup, air conditioning and idle speed.

Print this page


Have your say:

Your email address will not be published. Required fields are marked *