Circuit/System Testing: Notes

NOTE:

Use the schematic to identify the following:

Gateway isolated low speed GMLAN devices the vehicle is equipped with
Device and splice pack locations on the gateway isolated low speed GMLAN serial data circuit
The gateway isolated low speed GMLAN serial data circuit terminals for each device or splice pack

Ignition/Vehicle OFF, disconnect the harness connectors at the K56 Serial Data Gateway Module, ignition ON/Vehicle In Service Mode.
Test for less than 4.5 V between each gateway isolated low speed GMLAN serial data circuit at the K56 Serial Data Gateway Module and ground.
- If any serial data circuit is greater than 4.5 V
  Refer to Testing the Serial Data Circuits for a Short to Voltage .
- Go to next step: If all serial data circuits are less than 4.5 V
Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 2 min for all vehicle systems to power down.
Test for greater than 100 Ω between each gateway isolated low speed GMLAN serial data circuit at the K56 Serial Data Gateway Module and ground.
- If any serial data circuit is 100 Ω or less
  Refer to Testing the Serial Data Circuits for a Short to Ground .
- Go to next step: If all serial data circuits are greater than 100 Ω
Test for less than 2 Ω in the primary low speed GMLAN serial data circuit (circuit number 5060) end to end between the K56 Serial Data Gateway Module and X84 Data Link Connector terminal 1.
- If 2 Ω or greater
  Repair the open/high resistance in the low speed GMLAN serial data circuit.
- Go to next step: If less than 2 Ω
If equipped, inspect all gateway isolated low speed GMLAN splice packs for damage.
Repair the open/high resistance in the gateway isolated low speed GMLAN serial data circuit between the K56 Serial Data Gateway Module and the closest splice (or the closest gateway isolated low speed GMLAN device).