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:

Each device may need to be disconnected to isolate a circuit fault. Use the schematics and connector end views to identify all devices on the Powertrain CAN bus and each device's powertrain sensor bus enable circuit terminal.

Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the harness connectors at the K212 Gear Shift Control Module. It may take up to 10 min for all vehicle systems to power down.
Verify a test lamp does not illuminate between the powertrain sensor bus enable circuit terminal and ground.
- If the test lamp illuminates
1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the K20 Engine Control Module and all devices that share the powertrain sensor bus enable circuit.
2. Ignition ON/Vehicle In Service Mode.
3. Test for less than 1 V between the powertrain sensor bus enable circuit and ground.
  - If 1 V or greater, repair the short to voltage in the circuit.
  - Go to next step: If less than 1 V
4. Ignition/Vehicle OFF, reconnect the K20 Engine Control Module.
5. Verify a test lamp does not illuminate between the powertrain sensor bus enable circuit terminal and ground.
  - If the test lamp illuminates, replace the K20 Engine Control Module.
  - Go to next step: If the test lamp does not illuminate
6. Reconnect the first device that shares the powertrain sensor bus enable circuit.
7. Verify a test lamp does not illuminate between the powertrain sensor bus enable circuit terminal and ground.
  - If the test lamp illuminates, replace the device that was just connected.
  - If the test lamp does not illuminate and there are more devices to connect, connect the next device and repeat step 2.7 until there are no more devices to connect.
- Go to next step: If the test lamp does not illuminate
Ignition ON/Vehicle In Service Mode.
Verify a test lamp illuminates between the powertrain sensor bus enable circuit terminal and ground.
- If the test lamp does not illuminate
1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the K20 Engine Control Module and all devices that share the powertrain sensor bus enable circuit.
2. Test for infinite resistance between the powertrain sensor bus enable circuit and ground.
  - If less than infinite resistance, repair the short to ground in the circuit.
  - Go to next step: If infinite resistance
3. Test for less than 2 Ω in the powertrain sensor bus enable circuit 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
4. Reconnect the K20 Engine Control Module.
5. Ignition ON/Vehicle In Service Mode.
6. Verify a test lamp illuminates between the powertrain sensor bus enable circuit terminal and ground.
  - If the test lamp does not illuminate, replace the K20 Engine Control Module.
  - Go to next step: If the test lamp illuminates
7. Ignition/Vehicle OFF, reconnect the first device that shares the powertrain sensor bus enable circuit.
8. Ignition ON/Vehicle In Service Mode.
9. Verify a test lamp illuminates between the powertrain sensor bus enable circuit terminal and ground.
  - If the test lamp does not illuminate, replace the device that was just connected.
  - If the test lamp illuminates and there are more devices to connect, connect the next device and repeat step 4.9 until there are no more devices to connect.
- Go to next step: If the test lamp illuminates
Replace the K212 Gear Shift Control Module.