Circuit/System Testing

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

Inspect for an open Ign Switch fuse. The fuse should be OK.
- If the fuse is open, test the following circuits for a short to ground, if all circuits test OK, replace the BCM.
  - Battery positive voltage of the ignition switch
  - Accessory voltage
  - Off/Run/Crank voltage
  - Ignition 1 voltage
  - Accessory wakeup serial data (BCM output)
  - Run/crank ignition 1 voltage (BCM output)
Disconnect the harness connector at the ignition switch.
Verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.
- If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

IMPORTANT: The ignition switch component test must be preformed before proceeding with this test to verify the integrity of the switch.

Perform the ignition switch component test. The test should pass.
- If the ignition switch fails, replace the ignition switch.
Ignition OFF, disconnect the X1 harness connector at the BCM, test for less than 1.0 volt between the following circuit terminals of the BCM and ground.
- Off/Run/Crank voltage terminal 2
- Accessory voltage terminal 21
- Run Crank voltage terminal 14
- If greater than specified, test the circuit for a short to voltage.
Test for less than 1.0 ohm between the BCM and the ignition switch on the following circuit terminals.
- Off/Run/Crank voltage, BCM terminal 2 and ignition switch terminal 4
- Accessory voltage, BCM terminal 21 and ignition switch terminal 3
- Run Crank voltage, BCM terminal 14 and ignition switch terminal 1
- If greater than specified, test the circuit for open/high resistance
If all circuits test normal, replace the BCM.