Circuit/System Testing
WARNING: This page is about a different car, the 2023 GMC Sierra 3500 HD and 2023 GMC Sierra 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition/Vehicle - Off
- Disconnect the electrical connector:X1@T12 Automatic Transmission Assembly
- Connect a test lamp between the test points:Control circuit terminal 9@Component harness & Ground
- Ignition - On/Vehicle - In Service Mode
- Connect a 3 A fused jumper wire between the test points:9 V Reference circuit terminal 7 X1 (harness side) & 9 V Reference circuit terminal 7 X1 (component side)
- Connect a 3 A fused jumper wire between the test points:Signal circuit terminal 4 X1 (harness side) & Signal circuit terminal 4 X1 (component side)
- Perform the scan tool control function:High Side Driver 2 - On and Off
Verify the test lamp turns On and Off.
- If the test lamp is always Off
- Ignition/Vehicle - Off & Remove - Test lamp
- Disconnect the electrical connector:K71 Transmission Control Module
- Test for infinite resistance between the test points:Control circuit terminal 9@Component harness & Ground
- If less than infinite resistance - Repair the short to ground on the circuit.
- Go to next step: If infinite resistance
- Test for less than 2 ohms between the test points:Control circuit terminal 9@Component harness & Terminal 49@Control module harness
- If 2 ohms or greater - Repair the open/high resistance in the circuit.
- If less than 2 ohms - Replace the component:K71 Transmission Control Module
- If the test lamp is always On
- Ignition/Vehicle - Off & Remove - Test lamp
- Disconnect the electrical connector:K71 Transmission Control Module
- Ignition - On/Vehicle - In Service Mode
- Test for less than 1 V between the test points:Control circuit terminal 9@Component harness & Ground
- If 1 V or greater - Repair the short to voltage on the circuit.
- If less than 1 V - Replace the component:K71 Transmission Control Module
- Go to next step: If the test lamp turns On and Off
- Ignition/Vehicle - Off & Remove - Test lamp
- Connect the electrical connector:X1@T12 Automatic Transmission Assembly
- Remove the component:Automatic Transmission Fluid Pan
- Disconnect the electrical connector:X177
- Connect a test lamp between the test points:Control circuit terminal 18@Component harness & Ground
- Ignition - On/Vehicle - In Service Mode
- Perform the scan tool control function:High Side Driver 2 - On and Off
Verify the test lamp turns On and Off.
- If the test lamp does not turn On and Off
Replace the component:Automatic Transmission Wiring Harness - Pass-Thru
- Go to next step: If the test lamp turns On and Off
- If the test lamp does not turn On and Off
- Ignition/Vehicle - Off & Remove - Test lamp
- Connect the electrical connector:x177
- Disconnect the electrical connector:
- Q77A Transmission Control Solenoid Valve 1
- Q77B Transmission Control Solenoid Valve 2
- Q77C Transmission Control Solenoid Valve 3
- Q77D Transmission Control Solenoid Valve 4
- Q77E Transmission Control Solenoid Valve 5
- Q77F Transmission Control Solenoid Valve 6
- Q77J Transmission Control Solenoid Valve 9
- Connect a test lamp between the test points:Control circuit terminal 1@Component harness@ & Ground
- Perform the scan tool control function:High Side Driver 2 - On and Off
Verify the test lamp turns On and Off.
- If the test lamp does not turn On and Off
Replace the component:Automatic Transmission Wiring Harness - Main/Solenoid
- Go to next step: If the test lamp turns On and Off
- If the test lamp does not turn On and Off
- Test or replace the component:
- Q77A Transmission Control Solenoid Valve 1
- Q77B Transmission Control Solenoid Valve 2
- Q77C Transmission Control Solenoid Valve 3
- Q77D Transmission Control Solenoid Valve 4
- Q77E Transmission Control Solenoid Valve 5
- Q77F Transmission Control Solenoid Valve 6
- Q77J Transmission Control Solenoid Valve 9
NOTE:
If unable to perform the scan tool control function due to Device Limits Exceeded and/or DTC Present, jumper the component B14A circuits between the component T12 connector and the X1 harness connector.