No Fourth Gear - D4

WARNING: This page is about a different car, the 2006 GMC Yukon XL, 2006 Chevrolet Suburban, and 2006 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

No Fourth Gear - D4

Checks	Cause
Fourth Clutch Components
Seals (527) (531)	Nicked or cut
Cup Plug (530)	Missing
Bolt (26)	Loose, broken, or missing
Piston (528)	Jammed
Spring Assembly (532)	Jammed
Retainer Ring (523)	Not seated
Friction Plates (525)	Worn or burned
Reaction Plates (526)	Worn splices
Housing (529)	Damaged or cracked
Overrun Clutch Components
Housing (504)	Broken
Reaction Plates (508)	Worn splines
Sun Gear (650)	Worn
1-2 Solenoid (313)	Stuck Off Pinched wire O-ring failure No voltage to the solenoid
PCM	No signal to the solenoid Failed
3-4 Shift Valve (308)	Stuck
Check the PCM for current DTCs.