Vehicle inspections are a very common thing on all cars that come through our shops and are a great way to keep the shop bays filled with profitable work. Have you ever thought about using your scan tool as part of the inspection process?
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Many shops have spent a lot of money on scan tools and are wondering where the return on investment (ROI) is. Other shops are thinking of buying a good scan tool or other diagnostic equipment and wondering if spending the money will make a profit. Maybe the scan tool has been sitting on the shelf catching dust and you wonder what good it is? Is it only useful for pulling codes? Well, a scan tool is just like any other tool in the shop, if it is used correctly it will make money.
The first thing that some techs and shop owners will say is, “I don’t have the time to do a scan tool test, and I do not want to start giving away diagnostic time.” Consider how much time you already invest in a vehicle inspection where you check all of the fluids, brakes, hoses, belts, lights and all of the other things that inspection entails. What would you say if you could hook up the scan tool, take a short test drive and analyze the stored data all within 15 minutes? If you want to move your business to something new and set your shop apart from the other shops up and down the street, then read on.
My Project
This project started about 15 years ago. I had been reading on iATN about techs using lab scopes to find hard to find problems. As I started studying this concept, I finally got up the nerve to invest some money in a lab scope. This tool opened up a new world of diagnostics to me. I learned to use the lab scope to analyze ignition systems which again opened up a whole new world of diagnostic possibilities to me. It wasn’t long until OBDII cars started coming to my shop and those cars all had data stream. Again, I was reading on iATN about technicians using scan tools to analyze driveability problems with great success. Some of those guys were able to use a scan tool to quickly find problems that were taking me a lot of time to find and many of these were problems I had been struggling with. This caused me to stop and think about the worth of scan tools and how using the data that is available in the data stream could save me a lot of time in my diagnostic procedures and in turn, make me a lot of money.
When selecting a scan tool for this type of work, I would suggest using a tool that is very portable. The tool needs to be able to capture data at a brisk rate and be able to display the data in graphical form so the selected data can be displayed in an order that makes it simple to analyze. It is also a must that this data be easily stored for later playback. Please do not try this type of analysis with a code reader or a scan tool that will only display numbers. You will drive yourself and your techs crazy trying to pick out small problems this way.
Two key things needed to sell service with a scan tool are first to understand fuel trim data and second to work out a test drive route where you or your techs can drive the same test drive on all cars. The test drive needs to be able to idle the engine, drive slowly for a short distance, do a wide open throttle (WOT) run up through at least one shift point and cruise for a short distance. By putting a vehicle in all of these different driving conditions, you should be able to pick out things like engine misfires, poor fuel supply (which could be either a restricted fuel filter, restricted injectors or a weak fuel pump) vacuum leaks, restricted air flow (intake or exhaust), misreporting Mass Air Flow sensors (MAF) or misreporting oxygen or air fuel ratio sensors.
Stop and think about the wealth of information that can be gleaned from the vehicle in such a short time. I think that you will find there is a host of other problems on vehicles other than broken CV boots, worn brakes or leaking struts and most of these problems we are not able to see with our eyes, or even feel with the seat of the pants, but can be found with a quick test drive while monitoring a few data PIDS (Parameter Identifiers) on our scan tools. Waiting for the check engine light to illuminate to tell you there is a problem with the engine or emission system is like waiting for the brakes to start grinding, or the brake pedal to hit the floor to signal a problem with the brakes.
Off to an Easy Start
Starting out with a scan tool inspection might be a little intimidating. I would suggest that you start watching fuel trim information as a place to start. A good way to get your feet wet with this concept is to start small and work from there. Start by hooking up your scan tool to known good cars and learn what good cars look like. Until you know what good is, you will not know what bad looks like. Start this new adventure in the shop by observing the long term and short-term fuel trim data, as well as the Idle Air Control (IAC) data at idle and different engine speeds. You will be amazed how many vacuum leaks you will find while you are sitting there in the shop.
It is a great idea to be able to graph this data so it can be printed out. When presenting your findings to the customer, you will find that using pictures and graphs will make the sale a lot easier, especially when there is no check engine light, and no perceived driveability problems.
Let’s start off with some data from a 2006 GMC Sierra K1500, 5.3, automatic transmission, with 120,000 miles on the odometer. There are no drivability problems or any check engine light. The scan tool was hooked up, the PIDS selected were RPM, loop status, long- and short-term fuel trims for both banks and throttle position in volts. These few PIDS will give me enough information to determine if there are any vacuum leaks or if there are other issues that will require the vehicle back for some diagnostic time. In the case of this Sierra, I do not like the way the long term fuel trims moved, so I will sell a basic diagnostic test drive to determine what the problem is. I suspect that the MAF is failing.
The next vehicle in the bay is a 2008 GMC Sierra K1500. The vehicle also is powered with the 5.3L engine and the odometer shows 87,000 miles have been traveled. The scan tool was hooked up and the PIDS selected were RPM, loop status, long and short term fuel trims for both banks and throttle position. The engine was started, idled and brought up to 2,500 rpm. In this case, I see nothing unusual about the data displayed. I am checking for a possible vacuum leak, but none were found. I did not net any sales on this inspection.
The next vehicle in the bay is a 1997 Ford F150. The vehicle is powered with the 4.6 OHC engine and the odometer reads just over 148,000. Again, this vehicle is in for a routine service and there are no check engine lights or driveability complaints. The usual data PIDS have been selected, the engine speed increased from idle to 2500 rpm, but on this vehicle the long term fuel trim movement has caught my eye. This vehicle needs to go on a test drive. I am suspecting the MAF is getting a little lazy and is misreporting its data.
Three well-maintained, late-model vehicles through the shop, no oil leaks, all have good brakes, shocks, tires, belts and hoses, the transmission oil and brake fluids are all nice and clean but down inside in the engine management system, problems are hiding on two of the three vehicles. The service writer has contacted the customers and sold some diagnostic time to get to the bottom of these hidden problems. Is this sort of service something that you have been missing on vehicles that come through your shop? Three vehicles through the shop, two problems found which will result in the sale of diagnostic time, then the sale of the parts and labor to fix the problem.
Out Of The Bay And On The Road
The first vehicle to test drive is the 2006 GMC K 1500 Sierra. The Sierra was taken out on a FRTD (flat rate test drive) while capturing data for a later review. Reviewing the data, I can see that the MAF sensor is not reporting properly. The two data PIDS that jump out at me are the engine load PID of 90 percent engine and the long term bank 1 & bank 2 where the long-term trim changes every time the engine load is changed.
On this vehicle I expect to see the load PID very close to 99 percent and the long-term fuel trim moving less than 10 percent with engine load changes. Since the load PID only went to 90 percent at a full throttle shift point and the long-term fuel trims are jumping between -19 percent and -6 percent and both banks are about the same, I think that we can call a MAF problem. If we take a look at the oxygen sensors, the voltage does not indicate a fuel delivery problem.
With a new MAF installed, the vehicle was taken out for another test drive to see if the fuel trims
To get to the bottom of the problem, we need to know what the actual blend of fuel is in the tank. Testing results found there was an actual alcohol content of 8 percent in the fuel tank. Looking at the scan data it shows the PCM has calculated the alcohol content to be 49 percent. This miscalculation is enough to cause the fuel trim problem that is displayed on the scan tool. While searching for any Technical Service Bulletin (TSB) listed for this problem, one popped up for a reflash to help out with this problem. In this case, the PCM software was upgraded to take care of this calculation problem.
We invest a lot of money in our diagnostic equipment, and it is only normal to want to earn a return by charging its use to our customers. But consider how much more you can add to your bottom line, as well as the experience you’ll gain, by using that expensive equipment on every customer’s car during your normal inspection process. Learn now to work smarter, not harder!
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