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 & All vehicle systems - Off
- Disconnect the electrical connector:X1@ T12 Automatic Transmission Assembly
- Ignition - On/Vehicle - In Service Mode
- Test for 8.3 to 9.6 V between the test points:9 V Reference circuit terminal 7 & Ground
- If less than 8.3 V
- Ignition/Vehicle - Off
- Disconnect the electrical connector:K71 Transmission Control Module
- Test for infinite resistance between the test points:9 V Reference circuit terminal 7@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:9 V Reference circuit terminal 7@Component harness & Terminal 7@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 greater than 9.6 V
- Ignition/Vehicle - Off
- Disconnect the electrical connector:K71 Transmission Control Module
- Ignition - On/Vehicle - In Service Mode
- Test for less than 1 V between the test points:9 V Reference circuit terminal 7@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 between 8.3 and 9.6 V
- Ignition/Vehicle - Off
- Install & Setup - EL-38522 Variable Signal Generator
- Voltage - 5 V
- Frequency - 5, 000 Hz
- Duty Cycle - 10%
- Black lead@Ground
- Red lead @Signal circuit terminal 4
- Ignition - On/Vehicle - In Service Mode
- Verify the scan tool parameter:Transmission OSS = 3, 615 to 3, 690 RPM
- If not between 3, 615 and 3, 690 RPM
- Ignition/Vehicle - Off
- Disconnect the electrical connector:K71 Transmission Control Module
- Ignition - On/Vehicle - In Service Mode
- Test for less than 1 V between the test points:Signal circuit terminal 4@Component harness & Ground
- If 1 V or greater - Repair the short to voltage on the circuit.
- Go to next step: If less than 1 V
- Ignition/Vehicle - Off
- Test for infinite resistance between the test points:Signal circuit terminal 4@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:Signal circuit terminal 4@Component harness & Terminal 14@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
- Go to next step: If between 3, 615 and 3, 690 RPM
- Verify the scan tool parameter:Transmission Output Speed Sensor Direction Signal =.02 ms
- If not the specified value
Replace the component:K71 Transmission Control Module
- Go to next step: If the specified value
- If not the specified value
- EL-38522 Variable Signal Generator - 600 Hz
- Verify the scan tool parameter:Transmission Output Speed Sensor Direction Signal = 0.17 ms
- If not the specified value
Replace the component:K71 Transmission Control Module
- Go to next step: If the specified value
- If not the specified value
- Ignition/Vehicle - Off & Remove - EL-38522 Variable Signal Generator
- Connect the electrical connector.X1@T12 Automatic Transmission Assembly
- Remove the component:Automatic Transmission Fluid Pan
- Disconnect the electrical connector:B14A Transmission Output Shaft Speed Sensor
- Ignition - On/Vehicle - In Service Mode
- Test for 8.3 to 9.6 V between the test points:9 V Reference circuit terminal 2 & Ground
- If not between 8.3 and 9.6 V
Replace the component:Automatic Transmission Wiring Harness
- Go to next step: If between 8.3 and 9.6 V
- If not between 8.3 and 9.6 V
- Ignition/Vehicle - Off
- Install & Setup - EL-38522 Variable Signal Generator
- Voltage - 5 V
- Frequency - 5, 000 Hz
- Duty Cycle - 10%
- Black lead@Ground
- Red lead@Signal circuit terminal 1
- Ignition - On/Vehicle - In Service Mode
- Verify the scan tool parameter:Transmission OSS = 3, 615 to 3, 690 RPM
- If not between 3, 615 and 3, 690 RPM
Replace the component:Automatic Transmission Wiring Harness
- Go to next step: If between 3, 615 and 3, 690 RPM
- If not between 3, 615 and 3, 690 RPM
- Test or replace the component:B14A Transmission Output Shaft Speed Sensor
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.