GM Service Manual Online
For 1990-2009 cars only

Checks

Causes

Detent Roller

Broken or disconnected

Detent Roller Pin

Missing, damaged

Detent Spring

Broken or disconnected

Indicator Linkage

Misadjusted

Manual Detent Pivot

Loose or missing

Manual Shaft

Flats not parallel

Manual Valve

Not engaged to detent lever

Internal Mode Switch (IMS)

Not properly adjusted