Circuit/System Testing

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, 2018 Chevrolet Suburban 3500 HD, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Ignition Off, remove the Q8 Control Solenoid Valve Assembly.
Connect the DT-47825-10 Jumper Harness between the vehicle wire harness electrical connector and the Q8 Control Solenoid Valve Assembly electrical connector.
Disconnect the B14A/B14C Transmission Input and Output Speed Sensor harness connector X3 at the Q8 Control Solenoid Valve Assembly. Ignition ON.
Test for 8.8 - 9.2 V between the 9 V reference circuit terminal B at the Q8 Control Solenoid Valve Assembly and ground.
- If not between 8.8 - 9.2 V
  Replace the Q8 Control Solenoid Valve Assembly.
- Go to next step: If between 8.8 - 9.2 V
Ignition Off, connect the red lead of the J-38522 Variable Signal Generator to the ISS signal circuit terminal A at the Q8 Control Solenoid Valve Assembly and ground at the transmission case.
Set the J-38522 Variable Signal Generator to the following specifications:
- Signal Switch to 8 V
- Frequency switch to 300
- Duty cycle switch to the 50 or the Normal position
Ignition On.
Verify the scan tool Transmission ISS parameter is between 760 - 785 RPM.
- If not between 760 - 785 RPM
  Replace the Q8 Control Solenoid Valve Assembly.
- Go to next step: If between 760 - 785 RPM
Verify there is no damage or misalignment with the machined teeth on the 1-2-3-4 and 3-5 clutch housing.
- If the machined surfaces are damaged or misaligned
  Repair or replace as necessary.
- Go to next step: If the machined surfaces are not damaged or misaligned
Replace the B14A/B14C Transmission Input and Output Speed Sensor.