Diagnostic Aids

WARNING: This page is about a different car, the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

A defective transmission output speed sensor (OSS) can cause inaccurate speed reading, creating faulty replicated output speed signal. Also, inspect the OSS for cracks, loose mounting, or damage.
If the speed sensor passes testing, refer to Testing for Intermittent Conditions and Poor Connections .