Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Use the schematics and connector end views to identify the control module's ground, B+, ignition, and Ethernet serial data circuit terminals.

Ignition/Vehicle OFF, disconnect the harness connectors at the K56 Serial Data Gateway Module.
Verify a test lamp illuminates between each of the ground circuit terminals and B+.
- If the test lamp does not illuminate
  Repair the open/high resistance in the ground circuit or ground connection.
- Go to next step: If the test lamp illuminates
Ignition ON/Vehicle In Service Mode.
If equipped, verify a test lamp illuminates between each of the B+ circuit terminals and ground.
- If the test lamp does not illuminate and the circuit fuse is good
1. Test for an open/high resistance in the B+ circuit.
  - If an open/high resistance is found, repair the fault on the circuit.
  - Go to next step: If an open/high resistance is not found
2. Verify the fuse is not open and there is voltage at the fuse.
- If the test lamp does not illuminate and the circuit fuse is open
1. Test for a short to ground in the B+ circuit.
  - If a short to ground is found, repair the fault in the circuit.
  - Go to next step: If a short to ground is not found
2. Replace the K56 Serial Data Gateway Module.
- Go to next step: If the test lamp illuminates
If equipped, verify a test lamp illuminates between each of the ignition circuit terminals, which has a fuse in the circuit, and ground.
- If the test lamp does not illuminate and the circuit fuse is good
1. Test for an open/high resistance in the ignition circuit.
  - If an open/high resistance is found, repair the fault in the circuit.
  - Go to next step: If an open/high resistance is not found
2. Verify the fuse is not open and there is voltage at the fuse.
- If the test lamp does not illuminate and the circuit fuse is open
1. Test for a short to ground in the ignition circuit.
  - If a short to ground is found, repair the fault in the circuit.
  - Go to next step: If a short to ground is not found
2. Replace the K56 Serial Data Gateway Module.
- Go to next step: If the test lamp illuminates
Ignition/Vehicle OFF, disconnect the harness connectors at the K179 Automated Driving Mapping Module.
Ignition ON/Vehicle In Service Mode.
Test for less than 1 V between each of the Ethernet bus 3 circuit terminals and ground.
- If 1 V or greater
  Repair the short to voltage in the circuit.
- Go to next step: If less than 1 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 10 min for all vehicle systems to power down.
Test for infinite resistance between each of the Ethernet bus 3 circuit terminals and ground.
- If less than infinite resistance
  Repair the short to ground in the circuit.
- Go to next step: If infinite resistance
Test for infinite resistance between the pair of the Ethernet bus 3 circuit terminals.
- If less than infinite resistance
  Repair the short together in the circuits.
- Go to next step: If infinite resistance
Test for less than 2 Ω in each of the Ethernet bus 3 circuits end to end.
- If 2 Ω or greater
  Repair the open/high resistance in the circuit.
- Go to next step: If less than 2 Ω
Replace the K56 Serial Data Gateway Module.
Reconnect the harness connectors at the K179 Automated Driving Mapping Module.
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 10 min for all vehicle systems to power down.
Ignition ON/Vehicle In Service Mode.
Verify DTC B1A1D does not set.
- If the DTC sets
  Replace the K179 Automated Driving Mapping Module.
- Go to next step: If the DTC does not set
All OK.