NORMAL Inhibits Which Result in a Blinking PRNDL

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

High Engine Speed NEUTRAL to Range Shifts
When a NEUTRAL to DRIVE or NEUTRAL to REVERSE shift is made, when engine RPM is high, the shift will be inhibited to NEUTRAL. The TCM has torque management capability and will attempt to slow the engine to a point where it will make the requested shift.
High Throttle or Torque Direction Change Shifts
REVERSE to DRIVE, DRIVE to REVERSE, NEUTRAL to DRIVE, and NEUTRAL to REVERSE shifts, where throttle position is greater than 25 percent, will be inhibited to NEUTRAL. The TCM has torque management capability and will attempt to slow the engine to a point where it will make the requested shift.
Four-Wheel Drive Transfer Case in NEUTRAL
If the four-wheel drive transfer case is shifted into NEUTRAL while the transmission is in DRIVE or REVERSE, the transmission will continue to the commanded range until output speed is low, at which point NEUTRAL is commanded.

If the driver attempts to shift the transmission from NEUTRAL to DRIVE or NEUTRAL to REVERSE, with the transfer case in NEUTRAL, the PRNDL display will blink immediately.
High Output Speed Direction Change Shifts
REVERSE to DRIVE, DRIVE to REVERSE, and NEUTRAL to REVERSE shifts, initiated above 300 RPM output speed, will be inhibited to NEUTRAL.
Low Automatic Transmission Fluid (ATF) Level
Low ATF level is caused by insufficient transmission fluid and lack of initial pump prime, caused by refilling the transmission.
Extremely Low ATF temperature
A shift out of NEUTRAL when the ATF temperature is below -45°C (-49°F) may be inhibited.