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 malfunctioning speed sensor could cause DTC P2771 to set.

Verify that the input speed sensor (ISS) and the OSS are functioning properly.
In 3rd gear at approximately 64 km/h (40 mph), command TCC ON. If functioning properly the OSS will track ISS and the engine RPM. If not refer to DTC P0716 or P0717 for the ISS and DTC P0722 or P0723 for the OSS.
If the speed sensors pass testing, refer to Testing for Intermittent Conditions and Poor Connections .