Conditions for Setting the DTC
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The power-train control module (PCM) or body control module (BCM) diagnose a condition that is preventing the engine from performing traction control functions, and sends a serial data message to the EBCM indicating that torque reduction is not allowed. The PCM or BCM will typically set a DTC and the EBCM will set this DTC.