Circuit / System Testing

WARNING: This page is about a different car, the 2021 GMC Sierra 3500 HD and 2021 GMC Sierra 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

Ignition / Vehicle & All vehicle systems - Off
Disconnect the electrical connector: X5K9 Body Control Module
Ignition - On / Vehicle - In Service Mode
Verify a test lamp turns On between the test points: B+ circuit terminal 3 & Ground
- If the test lamp does not turn On and the circuit fuse is OK
1. Ignition / Vehicle - Off & Remove - Test lamp
2. Test for less than 2 ohms between the test points: B+ circuit terminal 3 & Output terminal @ Fuse
  - If 2 ohms or greater - Repair the open / high resistance in the circuit.
  - If less than 2 ohms - Verify the fuse is OK and there is voltage at the fuse.
- If the test lamp does not turn On and the circuit fuse is open
1. Ignition / Vehicle - Off & Remove - Test lamp
2. Disconnect the electrical connector: X7K9 Body Control Module
3. Test for infinite resistance between the test points: Control circuit terminal 1 & Ground
  - If less than infinite resistance - Repair the short to ground on the circuit.
  - If infinite resistance - Replace the component: K9 Body Control Module
- Go to next step: If the test lamp turns On
NOTE:
It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.
Ignition / Vehicle & All vehicle systems - Off
Disconnect the electrical connector: S3 Transmission Shift Lever
Test for less than 10 ohms between the test points: Ground circuit terminal 2 & Ground
- If 10 ohms or greater
1. Disconnect ground terminal.
2. Test for less than 2 ohms between the test points: Ground circuit terminal 2 & Ground
  - If 2 ohms or greater - Repair the open / high resistance in the circuit.
  - If less than 2 ohms - Repair the open / high resistance in the ground connection.
- Go to next step: If less than 10 ohms
Connect a test lamp between the test points: Control circuit terminal 1 & Ground circuit terminal 2
Ignition - On / Vehicle - In Service Mode
Perform the scan tool control function: Brake Transmission Shift Interlock Solenoid Actuator
Verify the test lamp turns On and Off.
- If the test lamp is always Off
1. Ignition / Vehicle - Off & Remove - Test lamp
2. Disconnect the electrical connector: K9 Body Control Module
3. Test for infinite resistance between the test points: Control circuit terminal 1 @ Component harness & Ground
  - If less than infinite resistance - Repair the short to ground on the circuit.
  - Go to next step: If infinite resistance
4. Test for less than 2 ohms between the test points: Control circuit terminal 1 @ Component harness & Terminal 6 X7 @ Control module harness
  - If 2 ohms or greater - Repair the open / high resistance in the circuit.
  - If less than 2 ohms Replace the component: K9 Body Control Module
- If the test lamp is always On
1. Ignition / Vehicle - Off & Remove - Test lamp
2. Disconnect the electrical connector: K9 Body Control Module
3. Ignition - On / Vehicle - In Service Mode
4. Test for less than 1 V between the test points: Control circuit terminal 1 @ Component harness & Ground
  - If 1 V or greater - Repair the short to voltage on the circuit.
  - If less than 1 V - Replace the component: K9 Body Control Module
  - Go to next step: If the test lamp turns On and Off
5. Test or replace the component: S3 Transmission Shift Lever