Over the years, the bread and butter in the automobile repair shop has been regular service and repair of vehicles. The first thing that comes to mind when we think of servicing a vehicle is doing an oil change or performing a brake job. As simple service has evolved into the more complex “scheduled services,” the need to start hooking up a scan tool and see what is hiding behind door one, two or three is very important.
There are always those vehicle inspections that management keeps shoving down our throats, too. Now on the other hand, have you noticed that the vehicles we work on today are requiring less and less service and maintenance than they did even 10 years ago? So why not start using the electronic diagnostic equipment that is sitting in our toolboxes to make life in the bay a little easier? I don’t think a scan tool will ever replace the need for a well-trained technician that is proud of their craft, but it will sure help them out.
More uses than ever
Over the years, I have made many learning projects in my shop, which required the use of scan tools. Things like understanding fuel trim and how to use the data to point toward drivability problems, or the use of the scan tool to analyze charging system problems are two that come to mind, but I think the scan tool can be used in many other ways to bring easy cash to both the shop and the technician.
As the flood of technology gushes past our shops, are you aware of the gravy that is floating on top? By this, I am referring to the amount of resources available to the scan tool user; not only data, but the bi-directional controls of the tool. Late-model vehicles have data stream for most everything on the vehicle: lights, cruise control, climate control, antilock brakes, traction control, stability control and the list goes on and on. Every electronic control module has data and will store diagnostic trouble codes, which can be a gold mine in the hands of an experienced scan tool user. So why should you be hooking up a scan tool to a seemingly good working vehicles? Let me give an example.
The vehicle in the shop is a 2011 GMC Terrain. Under the hood is a 2.4L gas direct injected (GDI) engine. There are 67,000 miles showing on the odometer; the vehicle is well maintained, drives great and has no known problems. I work in a small independent shop, and my scan tool of choice for a job like this is an aftermarket scan tool, which will hook up quickly and communicate with most modules on the vehicle. I also have OE scan tools for the hard-to-fix problems.
With the scan tool hooked to the vehicle, my first stop is the screen shown in Fig. 2, the menu of modules. This allows several different choices, but in the upper left corner is an option labeled “code scan.” By choosing this option, the scan tool will poll all available modules on the vehicle and report any diagnostic trouble codes that have been stored in those modules. Please don’t think if there are some codes stored, the scan tool is indicating the needed parts for the job. The diagnostic trouble codes (DTCs) only point to a place to start, or you might say they will give the technician a direction to start their process of problem analysis. In this case, the technician is only using the scan tool as a tool to sell service or needed repairs.
Think of the possibilities the scan tool gives the technician by being able to look in all modules for lurking problems. Since most vehicles use a module to operate the lighting system, a DTC will be set if something as simple as a light bulb is not functioning properly. How easy is it to sit in the front seat and have the scan tool tell you there is a stop light bulb out? I like this!
Back to the scan tool data. This DTC check takes about one or two minutes on this vehicle. The data displayed in Fig. 3 shows the report from all modules. In this case there are two modules with DTCs stored — the airbag module and the lift gate module.
The next screen, Fig. 4, shows each module, and the DTCs that are stored. The DTCs stored in both modules are U-codes, which are communication codes. At this point, I will not peruse these, since there are no reported problems with the components these modules control.
While we are browsing through the different scan tool functions, let’s stop and take a peek into the Body Control Module (BCM) and see what information is available. Fig. 5 shows a lot of different areas to access information. At the top left is the charging system data. This vehicle has a smart charging system and using the scan tool data is a great way to start a charging system problem analysis. Fig. 6 is a screen shot of the data available for the charging system. This can be very valuable information when testing for a charging system problem. Unless the technician knows for certain the BCM has commanded the generator on, any other testing can be a waste of time.
Each year as new vehicles arrive there is always a change in technology, and I would rather work on a late-model vehicle than a 20-year-old vehicle. I love using a scan tool and the vehicle data that is displayed. This is another reason I want to hook up a scan tool to every car that is in my shop for any major service. The scan tool in the hands of an experienced person can give a heads up to problems that are lurking in the wings, but have not reared their ugly heads.
Fig. 1: A six speed automatic transmission, with all-wheel drive comprises the powertrain. The odometer is showing 67,000 miles have been traveled.
Fig. 2: Each of these modules has a possibility of a problem. By clicking the “code scan” button in the upper left, the scan tool will do a code scan on all the available modules on the vehicle.
Fig. 3: With the information on this screen, it is easy to see which modules have any diagnostic trouble codes. The only diagnostic trouble codes that turn on the check engine light are emission related codes. A DTC stored in any other module will NOT turn on the CEL unless it is an emission related DTC.
Fig. 7: By using this data when working on a fuel pump problem should make the diagnostic process both fast and accurate.
Fuel pump testing with a scan tool?
Going back to Fig. 2, the main data screen, selecting the fuel pump option will display the data shown in Fig. 7. With this data, the technician can tell if the fuel pump is being commanded on, and there is also data about the commanded and actual fuel pressure. Wow, this is way cool! Is the fuel pump doing its job or not? The three pieces of information I really love is the fuel pump command in percent and the long-term and short-term fuel pump trim. The scan tool will tell us how hard the pump is working, and what has to be done to the pump to keep up with the demand of the engine. This is very good information if we are working on a fuel delivery problem. This data beats having to use a mechanical gauge any day. This data, combined with the fuel trim data, will nail down a fuel delivery problem right from the comfort of the front seat of the vehicle.
Using a scan tool without the help of service information can be a little misleading at times, especially if the technician doesn’t understand what the different Parameter Identifiers (PIDs) mean. Fig. 8 is a page from the MotoLOGIC® service information. By using service information along with the scan tool data, your analysis of problems will be quicker and more accurate.
Serve your customer, make some money
Why should we be hooking up a scan tool to vehicles when we do a major service? When doing a major service on most late-model vehicles, the lighting system is controlled by an electronic module. Here again, these modules have data streams and will store diagnostic trouble codes. An inspection of the lighting system, both internal and external can be performed with a scan tool. Fig. 9 is the data stream from the interior lights. Any light bulb that is not working correctly will code and this also makes checking stop lights easier. The data stream in Fig. 10 is the place to start when the need to verify any switch operation for the exterior lighting system. In the scan data on this GMC Terrain, every switch in the lighting system has a PID, and by watching the scan data, the technician can see if the switches are working.
How about bidirectional control of components? So far, I have not mentioned this function of the scan tool. The use of the scan tool to control components is a very important function. In the case of the lighting system, when working on the turn signals, by using the scan tool to control the signal functions, you will be able to verify if the module is capable of controlling the component or not. This is a great way to get a diagnostic direction before you start removing parts to do pinpoint testing.
Radio and entertainment system problems are always interesting to analyze. Since the radio is on the data bus, the scan tool has access to the component, and is also a great place to go for information. Fig. 11 is a screen shot of the data stream from the radio on this Terrain. If there is any question about what the scan tool data means, take a look at your information system. Fig. 12 is a page from MotoLOGIC® service information and shows what each of the data PIDs mean.
A discussion of using a scan tool would not be complete without a look at fuel trim data from the engine. For any technician working on a drivability problem, the use of fuel trim data is by far the best place to start. Any problem with the calculations of the air/fuel ratio will show up in the fuel trim data. I took this 2011 Terrain out on a quick flat rate test drive (FRTD) as part of the service. This engine is a GDI engine, most of which have problems with carbon building up on the intake valves. One great way to verify proper engine breathing in an engine like this is with scan data. The scan data captured in Fig. 13 shows the engine is operating properly.
Scheduled services are intended to get the vehicle into our bays so the vehicle can be inspected. Why limit the inspection to things we can only see with our eyes? Many shops have a lot of money tied up in scan tools, and without the proper training and practice, those tools will only sit on a shelf and collect dust.
Why not put the tools to good use? Instead of only pulling them out when a problem car is sitting in your bay, use them to sell service and bring your shop up a step or two from those shops down the street.
