GM/Detroit 6.5L – TECH 1 “SCAN” TOOL – Test Mode

After completing the OBD, you can enter the Tech 1’s “Test Mode.” This mode offers a variety of testing and data compilation options, as shown in figures 6-24 and 6-25.
These options are described below.
• FO: Data List — this option displays the data
parameters for identified data pairs.
• F1: Field Service — this option grounds terminal “B” of the DLC. This puts the PCM in Field Service mode. The “Service Engine Soon” lamp will flash any stored codes or loop status.

F2: DTC — this option displays Diagnostic Trouble Codes (DTC) stored in the PCM. Both current and history codes are displayed, from lowest to highest.
• F3: Snapshot — this option takes a “snapshot” of data and stores it for later retrieval. This is particularly useful for diagnosing intermittent conditions.
• F4: Misc Test — this option access a variety of miscellaneous tests. The number of tests varies, depending on system capabilities.

The Data List’ DTC’ and Snapshot options are further described on the following pages. For instructions on other Miscellaneous Tests and other Tech 1 options, consult the Tech 1 Operator’s Manual.

The Data List mode can be used to view the data param­eters for various engine functions. This data can be compared against the typical or normal data parameters. Select Data List by pressing the FO key at the Test Mode menu (see figure 6-24).

After selecting data list, a screen allows you choose which system’s data you want to view (figure 6-26). The choices are engine, transmission, or both.

Data Pairs
After you choose the data list system(s), the Tech 1 displays data list information in pairs. One scan position will appear at the top of the screen with its data value immediately underneath in the appropriate units. The second scan position will appear below the upper one, as shown in figure 6-27.

The Mass Storage Cartridge is preprogrammed with data pairs. You can scroll forward an backward through the list of predefined data pairs by using the YES and NO keys.

You can also create your own pair by locking either of the pair elements and scrolling the other entry until a new scan position is reached. To create your own data pair, use the following procedure.

1. With a data pair displayed on the Tech 1 screen, press the FO key. An asterisk will appear to the left of the uppermost parameter’s data (figure 6-28), This asterisk indicates that the parameter is locked.

2. Pressing the YES and NO keys will cause the bottom parameter to scroll.

3. To lock the bottom parameter, you must first unlock the top parameter. Do this by pressing the F1 key. The asterisk next to the top param­eter data will disappear.

4. With the top parameter unlocked, press the F1 key again. An asterisk will appear next to the data of the bottom parameter (figure 6-29).

5. With the bottom parameter locked, use the YES and NO keys to scroll the top parameter until a desired position is found.

6. To unlock the bottom parameter, press the FO key.

Only one parameter can be locked at a time. Also, the data pairs you create cannot he held permanently. If you unlock a fixed parameter and begin scrolling, you will return to the preprogrammed pairs.

Typical Tech 1 “Scan” tool data is provided in the chart below.

Selecting F2: DTC from the Test Mode menu accesses Diagnostic Trouble Codes. The screen will prompt you for the type of codes you want to view (figure 6-30).

Codes are identified as either current (C) or history (H). Current codes indicate a present fault; history codes indicate a fault that existed at one time but is not now present.

Codes are displayed one at a time. The Tech 1 will scroll automatically through the list of codes.

The Snapshot option is accessed by pressing F3 from the Test Mode menu. Snapshot is used to capture and store information.

Depending on the snapshot mode, you can press a key to mark a “trigger point.” This trigger point serves as the reference point for the Tech 1 to analyze data. This data can be replayed and studied to help in locating current and intermittent problems.

The snapshot function provides numerous capabilities that allow you to:
• Store data parameters and trouble codes before and/or after a problem occurs
• Observe current data as it is being stored
• Store from 75 to 400 data samples, depending on the system
• Store time and position indexes for each data stream
• Save data for up to 24 hours with no external power source applied
• Select manual or automatic triggering
• Select different trigger points
• Store and/or print captured data on a variety of sources, depending on system options


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