General Motors Tech2 User Guide
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When performing this test, you must also perform the Selectable VCI test (option F4 on the
self-test menu). First install the Burndy loopback adapter into the VCI 26-pin connector,
which does not require the cable. Once you select “Selectable VCI,” select the “More
Tests” soft key. In the new submenu, select “F6: VCI TPU”. If the VCI passes the test, all
the TPU channels will display a Pass indicator as shown in the example at the top of the
next page.
Testing Status
TPU0 Pass
TPU1 Pass
TPU5 Pass
TPU12 and 15 Pass
TPU13 and 14 Pass
The two TPU inputs that the CANdi module requires are TPU12 and TPU15, which enable
the module and detect its presence. If TPU12 and 15 do not appear on the screen, then
they are defective in the VCI module and the VCI is failing to properly enable the CANdi
module. If the above test passes, you must repeat the same test with the Burndy loopback
adapter at the end of the cable. The setup is the same as if you were plugging into a
vehicle without the CANdi module connected and with the loopback adapter at the end of
the cable. Then you must run the VCI TPU test. If the example above appears (TPU13 and
14 are missing in this test because these I/Os don’t go through the cable), then the cable is
also fine. However, if TPU12 and 15 are missing, then the cable is defective.
4. Verify that the DLC cable (also known as the ALDL, J-1962, or OBDII interface cable) is
functioning properly and then proceed to step five. Replace the DLC cable if it does not
function properly. Call the ACDelco Aftermarket Support Center at 1-888-212-8959 for
more information if you have trouble with this test.
5. Connect the CANdi module to the Tech2. Connect the system (Tech2 and CANdi
module) to a vehicle and power on the Tech2. Verify that the LED on the CANdi
module is flashing.
• If the LED does not flash or light up at all, it may be defective and you should
proceed to step six.
• If the LED is not flashing but illuminated, a bad ground may exist somewhere. The
grounding problem could be due to a defective ALDL (J-1962) female interface on
the vehicle. Power the Tech2 through an AC/DC power supply and connect the 12-
pin ALDL connector. If this fixes the problem with the CANdi (the LED is flashing),
then the vehicle has a grounding problem and the CANdi module is OK.
• If the LED is flashing while connected to the vehicle, but the CANdi module still has
a problem, proceed to step six.
6. If problems persist with the CANdi module, and the Tech2 recognizes the interface,
perform self-test diagnostics on the CANdi module. Select CANdi Diagnostics from the
Tool Options menu to see the CANdi Diagnostics menu. This menu allows you to
display POST results, or request the CANdi module to perform a self-test. Refer to the
main PCB self test for more information.
If a diagnostic test fails, contact the ACDelco Aftermarket Support Center at 1-888-212-
8959 before returning the CANdi module. If a known problem with a software version is
identified, ACDelco Support will inform you to update Tech2 software with the correct
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