No Engine Braking in First, Second, and Third Gear

WARNING: This page is about a different car, the 2007 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.

Check	Causes
DEFINITION: A large engine RPM increase and forward vehicle speed decrease do not immediately occur when the transmission is shifted from Overdrive or fourth gear in Drive range to either first or second gear, manual second.
Control Valve Body Accumulator Assembly	3-4 shift valve stuck released Missing or stuck low pressure control valve 4-5 shift valve and/or 4-5 control shift valve stuck released 1-2 shift valve stuck released 2-3 shift valve and/or 2-3 control shift stuck released