Scan tool graphical data as recorded and viewed through a personal computer has been around for some time, but hasn't been very user friendly for the working technician. I have memories of finding an injector problem on a early injected GM S10 pickup that had eluded the oscilloscopes of the day many years ago using an OTC scan tool and a product called EZ-Event.

Now, 15 years later, this approach to data retrieval is a must!

Taking information from your scan tool and displaying it into an easy-to-understand live sensor graph will help to ensure that no intermittent sensor problems go unnoticed. Lab scopes are great, but lack some record ability when trying to look at many parameters at once.

For many years we have used the scan tool to pull codes, check prom numbers and troubleshoot the vehicle. Many techs have been accused as being a "scanner tech" as they use this tool for everything they do.

But do we use this tool to its full potential? More than likely, the answer is "no!" We must understand the basic tool before taking it to the next step, which is graphical display.

Software and support interfaces enable the technician to detect the problem, view it much more closely and print out the detailed values of a problem sensor. These computer programs help eliminate the limitations of your scan tool. You may now store as much information as you need. This becomes very beneficial if you need to look at many specific sensors at one time. Once a spike is seen in one of the sensors, you may freeze the graph and expand the area to show actions before and after the spike.

Another great feature is being able to print all sensors in a spread sheet format that allows you to quickly pinpoint the sensor that started the chain reaction.

Example: A 1998 Ford Crown Victoria may display more than 400 data paramaters (PIDS)!

Also diagnostic printouts impress customers and makes it easier to sell service. The printouts facilitate service in several ways:

• They have a high tech look. This is impressive to the consumer and helps persuade customers that they're getting their money's worth.
• They provide authoritative diagnostic printouts of results. People trust computers more than they trust people!
• They enhance the professional mystique of the technicians using them. To the customer, anyone capable of using such a sophisticated devise must really know what he is doing and must really understand high-tech cars.

Merchandising service using the diagnostic printout
Diagnostic printouts can be used to help sell repairs. To maximize the effectiveness of the printout, your shop has to think in terms of putting on the best possible show. You could start with a customized computer paper with your shop name and logo screened into every page. This page contains the customer's name and address and can include various information about your shop.

To show the effect of the graphical scan tool software, we will use the following case studies:

Case Study 1 - Defective ECM?

This example of graphical data shows an ECM/PCM problem that may have been difficult to analyze using digital data alone. The graphs show very sharp and unusual change indicating a defective ECM.
Figure

Graphical Line Characteristics:
Since a graph line is a time line, vertical changes indicate changes that may be too fast to be physically possible.

When a line changes direction, pay attention to the way it makes a turn. Is the line sharp or rounded? Does the inside angle vary or remain constant? Does the amplitude of the line remain the same, change randomly or repeat?
Figure

Case Study 2 - A Graphical Repair!

The transmission had been recently rebuilt by a local transmission shop and sent to a local repair shop for Mil problem after rebuild. Repair shop checked codes and replaced TCC solenoid and ECM. The problem was still there.

While running the car on a dynomometer, the problem was easy to duplicate. After running 40-45 mph for a couple of minutes, the check engine lamp came on. With every occurrence, the same DTCs were set.

Using VT-100 mode provides a large list of parameters to view. However, it is still an alphanumeric display.

With more parameters to focus on, the intermittent problem becomes buried in a large list of data.

Circuit Description:
Figure

Power from the fuse is routed through the brake switch to the TCC line switch. This switch closes in second and third gear, providing power to the TCC solenoid. Each quad driver module in the ECM has a sense line and a fault line. When the TCC is commanded on, the voltage on the sense line is low, and when the TCC is commanded off, the voltage on the sense line is high.

DTC 26 sets when the ECM is commanding a controlled component on, and the voltage on the sense line is high, or if the component is commanded off and the voltage on the sense line is low. This can be monitored by watching the QDM fault line on the scan tool. High = Fault; Low = OK.

By studying the wiring diagram and using the graphed information shown, the problem is easily solved.

Look at the faults indicated by the QDM sense line. The ECM is expecting to see battery voltage at the sense line. With every QDM high reading, the ECM is seeing low voltage.
Figure

Remember power is supplied to the TCC through the brake switch. However, the brake switch reading consistently shows open. With the use of graphed scan data we have eliminated several problems and are left with two possibilities:

1 = Open TCC Pressure Switch (2nd gear switch)

2 = Poor Connection at the ECM

A quick check with a voltmeter confirmed that indeed there was a continuity problem with the inline pressure switch.

A scan tool software graphics program will allow you to display, analyze and print vehicle data using the scan tool of your choice. Most can display scanner data in test or graphic formats. These programs can be used to display live engine data, review a snap shot or recall a previously saved file. This makes displaying and analyzing data parameters quick and easy.

You may :

• Display scanner data "live" on a PC with the vehicle running.
• Transfer, display and save a previously recorded scanner movie to the PC.
• Analyze data from a recalled file.
• Automatically find suspected intermittent sensor or ECM output problems from recorded data using the snap shot playback.
• Use the VT1000 mode to look at live scanner data and operate the scanner from your PC.
• Print copies of vehicle data in the text or graphic format to document repairs.
• This is the next step in scan tools for the technician of today!

Jim Linder is owner of Linder Technical Services, an automotive technician support facility in Indianapolis. For more information on these topics, call (317) 487-9460, or visit his Web site at http://lindertech.com.

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