Circuit/System Verification

WARNING: This page is about a different car, the 2013 Cadillac XTS. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Use the schematic to identify the following:

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

Attempt to communicate with all devices on the low speed GMLAN serial data circuit. Refer to Data Link References .
Verify which devices are communicating on the low speed GMLAN serial data circuit.
- If only one device is not communicating
  Diagnose that device only. Refer to DTC U0100-U02FF .
- If one or more devices are communicating but not all
  Refer to Circuit/System Testing - Testing the Serial Data Circuit for an Open/High Resistance .
- If none of the devices are communicating
Ignition OFF, all access doors closed, all vehicle systems OFF, all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the scan tool from the X84 Data Link Connector. The following tests will be done at the X84 Data Link Connector. It may take up to 2 minutes for all vehicle systems to power down.
Test for less than 10 Ω between the ground circuit terminal 5 and ground.
- If 10 Ω or greater
1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, repair the open/high resistance in the ground connection.
- If less than 10 Ω
Ignition ON.
Test for less than 4.5 V between the serial data circuit terminal 1 and ground.
- If 4.5 V or greater
  Refer to Circuit/System Testing - Testing the Serial Data Circuits for a Short to Voltage .
- If less than 4.5 V
Ignition OFF, all access doors closed, all vehicle systems OFF, all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 2 minutes for all vehicle systems to power down.
Test for greater than 100 Ω between the serial data circuit terminal 1 and ground.
- If 100 Ω or less
  Refer to Circuit/System Testing - Testing the Serial Data Circuits for a Short to Ground .
- If greater than 100 Ω
Disconnect the appropriate harness connector at the first splice pack closest in the circuit to the X84 Data Link Connector.
Test for less than 2 Ω between the X84 Data Link Connector's serial data circuit terminal 1 and the splice pack harness connector's serial data input terminal.
- If 2 Ω or greater
  Repair the open/high resistance in the serial data circuit.
- If less than 2 Ω
Replace the splice pack.