Circuit/System Description

When a Slow-Down request is sent from OnStar® the vehicle communication interface module (VCIM) sends a serial data message to the engine control module (ECM) indicating that reduced vehicle speed has been requested. Once the request is active the ECM begins reducing engine torque to match requested vehicle speed and a REDUCED ENGINE POWER indications is displayed. No DTCs will be set during this process.

The ECM monitoring the serial data message for specific validity traits. If the ECM determines that the validity of the message is in error DTC P162B will be set.