Transmission Overheats (8L45 or 8L90)

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

Checks	Actions
Transmission Fluid Level	Inspect for incorrect (low) transmission fluid level. Inspect transmission for leaks.
Transmission Fluid Cooler and Cooler Lines	Inspect for obstructed air flow to transmission fluid cooler. Inspect for plugged or restricted transmission fluid cooler and/or cooler lines. Transmission Fluid Cooler Flow Test and Flushing Clean or replace transmission fluid cooler and/or cooler lines if necessary. If fluid cooler and/or cooler lines are okay, replace the Cooler Bypass Valve or Fluid Cooling Exchanger (model specific).
Engine Overheating	Engine Overheating
Torque Converter	Converter may be stuck OFF. Inspect torque converter circuit for debris or obstruction. Torque Converter Diagnosis Replace torque converter if necessary.
Automatic Transmission Fluid Temperature Sensor	Inspect for transmission fluid temperature sensor related DTC's due to inaccurate or faulty sensor.
Trailer Towing or Hauling	Ask customer about driving habits while towing. Improper trailer towing or vehicle load limits may have been exceeded. Towing should occur in Tow/Haul Mode.