Decoding Diagnostics: Take Control of Truck Repair With a Scanning System

With a fleet of trucks and construction vehicles, plumbers can save money by performing their own engine diagnostics. Learn what type of scanning equipment you should invest in.
Decoding Diagnostics: Take Control of Truck Repair With a Scanning System
The Innova 31703 ScanTool at work diagnosing a problem in the garage.

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The first on-board diagnostic (OBD) computers trace back to the late 1960s. Today, diagnostic scanning devices have become more sophisticated and less expensive.

What sort of diagnostic capability makes sense for the average installing professional’s fleet?

Gerry St. John, of operates an online business selling engine diagnostic equipment.

“Whether you call them scanners, code readers, scan tools or OBD devices, they amount to the same thing,” he says. “They read the error codes from the computer in your engine.”

The most basic and inexpensive scanners will read codes and erase some of them.

“These are often all you need if you want to do basic repairs, have a unit with your vehicle at all times or to hold an outside mechanic accountable,” says St. John.


However, more expensive scanners feature additional functionality. Some of the advanced features offered by more expensive readers include:

  • Antilock Brake System or Airbag capability: Allows the user to reset these codes.
  • On Screen Definitions: Lower cost units display a code, and provide a printed codebook. More expensive readers allow users to see full definitions on screen.
  • Printing ability: Results can be sent to a printer.
  • Live Data: Users can view engine sensors and performance in real time, as they drive.
  • Updatable: The reader can be updated online to keep up with changes in vehicle protocols.
  • Memory: Saves data in the scanner’s memory for later viewing.

Vehicle Identification Number (VIN) capability: Displays the VIN, allowing mechanics to more easily identify proper replacement parts.

The scan tool should match up to the protocol offered by the vehicle’s engine. Each protocol uses the same 16-pin connector, but employs a different type of pin activation.

“That problem is solving itself as older vehicles drop out of service,” says St. John. “Vehicles made after 2008 use a common OBD-II standard known as CANbus, which was introduced in 2003. You can find out what protocol your vehicle uses by checking for a label under the hood.”

St. John notes that as a general rule, low-cost universal readers have the most compatibility issues.

“They’re designed to work on the most common models and don’t offer the programming to cover all of the protocols from all vehicle manufacturers,” he says. “From my experience, about 98 percent of low-cost readers we sell work fine.”


However, St. John notes that the price gap between the top-end and low-end scanner has narrowed so significantly that higher-end scanners may sell for only a few dollars more than their low-end counterparts.

As the technology becomes readily available, basic OBD scanners can cost less than $20 and run up past $200, and are available through many sources and chain automotive equipment retailers. St. John’s best scanner retails for less than $40. High-end units using manufacturer’s proprietary software can cost quite a bit more.

St. John doesn’t deal in top-level garage scanners, which may cost thousands of dollars.

“I don’t generally recommend these for cars or light trucks unless you operate a garage as a business,” says St. John. “In addition to the cost of the equipment, you need to purchase manufacturer-specific software modules to get full functionality. Even my garage customers tell me that they may buy one of the expensive units and take turns using it while most mechanics in the shop rely primarily on less expensive scanners.”

Small shops can also use laptops to diagnose car engine problems. All that’s required is a connector – either a cable, Bluetooth or WiFi variety – a laptop and diagnostic software. These tools can allow the user to perform a wide range of functions, including real-time monitoring of engine rpm, mpg, coolant temperature and fuel pressure.

“The cables cost no more than hand scanners, but you need to have a laptop handy,” says St. John. “You can use free scanning software that can be downloaded from the Internet, such as OBD Gauge, OBD-II Logger and Real Scan, or you can buy professional packages such as Digimoto, PCMSCAN and ProScan. However, the most advanced software for your vehicle may be proprietary to the company that manufactured the vehicle.”


For plumbers who own larger trucks and construction equipment, code reading becomes more complex – and expensive.

Ed Dailey is the president of the Construction Equipment Maintenance Association and superintendent of Pyne Sand and Stone, a construction business located in Douglas, Mass.

“We just went through the exercise of deciding which computer diagnostics we wanted to invest in at our shop,” says Dailey. The shop’s fleet is divided between Mack and Caterpillar equipment. On the Cat side: four loaders, a backhoe, an excavator, a rock truck, a bulldozer and miscellaneous crushing/screening equipment. On the Mack side, Pyne operates three 10-wheel trucks and five tractors.

With 15 years in automotive maintenance, eight in construction, shop foreman Kyle Lahousse investigated the cost of diagnostics for the fleet. He notes that diagnostic equipment for construction equipment is largely proprietary, so universal scanners won’t provide diagnostic value.

“We investigated Caterpillar diagnostics, but much of our equipment is from older model years,” he says. “Unless you have newer units, the diagnostic equipment won’t provide a complete range of readings, so the cost of the scanners and software couldn’t be justified. We might consider that option when the fleet is upgraded.”


On the other hand, Lahousse wanted to ensure the shop could diagnose problems with the three Macks.

“If a truck is going to the garage, I have to figure in the labor cost of taking it to the garage, and another worker to take the driver back, the truck downtime and the cost of the repair,” he says. “It came down to buying a top-of-the-line universal scanner or buying a laptop scanner with dealer-specific software.”

Lahousse says he chose the dealer package and hasn’t looked back since.

“If I scan the engine with the dealer software, I won’t miss a code,” he says. “I can determine whether we need to send the job out, or whether it’s something like an electronic unit pump, which I stock and can change myself. The investment in scanners paid for itself on three repair jobs that we did in-house over a space of two weeks. However, if we’d had three different brands of trucks, it would have taken us longer to make up the cost.”

Lahousse says a knowledge of automotive diagnostics doesn’t translate automatically to large truck diagnostics.

“If you’re not already familiar with them, you’ll need the help of service manuals to understand all the codes,” he says.


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