Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
Inspect the ISS/OSS, harness, connector and control solenoid valve assembly for metallic debris and output shaft housing machined slots for damage or misalignment. Proper torque of the ISS/OSS mounting bolt is critical to proper speed sensor operation.