Types of auto diagnostic scanners

Written by richard ristow
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Types of auto diagnostic scanners
Mechanics have specialised computers and usually charge diagnostic fees. (Jupiterimages/Comstock/Getty Images)

A vehicle's dashboard contains a multitude of warning lights. This includes a general "Check Engine" light, as well as malfuction indicators for anti-lock brakes, tire pressure monitoring sensors, and air bags. Each of these diagnostic systems issues a trouble code once a problem is detected. Accessing these codes requires diagnostic hardware, and professional mechanics have a computer for this purpose. For the general public, however, there are smaller diagnostic code readers available. Each of these tools hook up to the same outlet in a vehicle.

On-Board Diagnostics

Using an on-board diagnostics (OBD) code reader depends on the year a vehicle was manufactured. Vehicles manufactured after 1996 go by OBD-II codes, whereas earlier cars and trucks go by OBD-I codes, and those codes can vary by manufacturer. OBD scanners cover a lot of areas in the vehicle, but particularly the engine and the fuel system. The fault codes can go from the drastic to the easy fix; parts of your engine may need more than routine maintenance or your gas cap might be broken.

Types of auto diagnostic scanners
OBD-II covers most engine systems. (Vintage Car Engine image by itsallgood from Fotolia.com)


Some scanners may be compatible with other diagnostic systems, but many of the cheaper ones are not. A basic OBD-II scanner will not read codes for anti-lock braking systems (ABS). While OBD-II scanners cover most vehicles manufactured after 1996, many of the ABS code readers cover only certain vehicles. When researching a possible code reader purchase, it is wise to consider the vehicles it can be used with and make certain the hardware is compatible.

Types of auto diagnostic scanners
Always diagnose brake problems immediately. (Car Brake image by Joelyn Pullano from Fotolia.com)

Tire Pressure Monitoring System

Tire pressure monitoring systems (TPMS) are not widely used as OBD-II codes, but soon will be. The Department of Transportation has mandated that all cars manufactured after 2008 be equipped with TPMS sensors. Although these monitors are no substitute for regularly checking tire pressure by hand, they can give a driver ample warning that there is a problem with a tire, which can help avoid a flat or a blowout. A TPMS scanner works very much the same way as OBD-II and ABS code readers. It interacts with a vehicle's computer, reads the trouble code, and can lead to a diagnosis.

Types of auto diagnostic scanners
Maintaining the right tire pressure will enhance gas mileage. (detail of a car tire image by Albert Lozano from Fotolia.com)

Air Bags

Air bags operate under the supplemental restraint system (SRS). Diagnostic tools for SRS trouble codes are scarcer than ABS readers. Of the few that are available, they tend to be specific to manufacturers, like BMW. Also, like the braking system, if there is a problem with air bags, it's best to leave the repair work to a trained professional. Air bags can require complex maintenance and be costly to fix, so reverse engineering a casual mistake can become expensive.

Multi-Use Scanners and Laptops

Technology develops at a pace that favours integration. Some day, diagnostic code scanners may become all-in-one tools. So instead of owning several readers, a home mechanic would have one tool for OBD, ABS, TPMS and other trouble codes. There are already several scanners that can multitask. Actron's CP9580 Auto Scanner, for example, can read both OBD and ABS codes. Presently, the more expensive the piece of hardware, the more access to vehicle diagnostics. Also, there is a way to bypass scanners altogether. A home mechanic can buy and download software packages and turn a laptop into a multilingual scan tool. However, a diagnostic cable with both a USB and a 16-pin data link connector would have to be purchased separately.

Types of auto diagnostic scanners
Diagnostics with a laptop allows for easier updating and upgrading as coding changes. (laptop image by Jorge Figueiredo from Fotolia.com)

Data Link Connection

No matter the diagnostic system, interfacing with a vehicle's diagnostic system requires access to the data link connection (DLC) in a vehicle. The only exception to this is with certain SRS scanners that require opening the vehicle's bonnet and locating a special 20-pin outlet. The regular DLC port's location, however, can vary by make and model of the vehicle but is usually located on the driver's side of the vehicle beneath the dashboard between the accelerator and the boot release. Once a diagnostic tool is attached, the hardware and the vehicle need to be turned on. The scanner will do the rest and automatically retrieve any awaiting trouble code.

Understanding Trouble Codes

A scanner's user manual should contain all the generic trouble code definitions as outlined by the Society of Automotive Engineers. Some codes, however, may be specific to a vehicle manufacturer, and definitions will likely not be available in a vehicle's owner manual. There are many websites on the Internet that can assist with finding code definitions, if you have lost your manual or cannot find the information you need.

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