Diagnostic Procedure
WARNING: This page is about a different car, the 2002 Toyota Avalon and 2001 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
Remove and check operation of SL solenoid. See SOLENOIDS under COMPONENT TESTS. If SL solenoid is okay, check and repair the valve body. See appropriate OVERHAUL article. If the valve body is okay, remove transaxle and check torque converter for overheating or damage. Replace torque converter as necessary. If torque converter is okay, repair internal transaxle malfunction.