Scan Tool Does Not Communicate With High Speed GMLAN Device

SCAN TOOL DOES NOT COMMUNICATE WITH HIGH SPEED GMLAN DEVICE

Modules connected to the GMLAN serial data circuit monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules.

Diagnostic Aids
The engine will not start when there is a total malfunction of the GMLAN serial data circuits while the engine is not running. The following conditions may cause a total loss of GMLAN data communication:
- Any of the GMLAN High Speed serial data circuits shorted to ground.
- Any of the GMLAN High Speed serial data circuits shorted to voltage.
- A short between GMLAN High Speed serial data circuits.
- An internal malfunction of a module on the GMLAN network that causes a short to voltage or ground.

TEST

Steps 1-2:

Step 3:

Step 4:

Step 5:

Steps 6-7: