CHRYSLER Collision Detection Bus System

The Chrysler Collision Detection (CCD) bus is a pair of twisted wires traveling from module-to-module between 5 modules receiving and delivering coded information. These modules are Air Bag Control Module (ACM), Compass/Mini-Trip Computer (CMTC), Mechanical Instrument Cluster (MIC), Remote Keyless Entry (RKE) module and Sentry Key Immobilizer Module (SKIM). Powertrain Control Module (PCM) and Transmission Control module (TCM) are not part of the body control system, but use the CCD bus to communicate.

The coded information identifies the message and its importance. When multiple messages attempt to access CCD bus at once, code assigns priority ranking.

The 2 twisted wires used by the CCD bus system are called bus "+" (positive) and bus "-" (negative). Both wires carry approximately 2.5 volts. The network consists of some modules with "bias" and some with "termination".

Bias is the part of the voltage divider network that places both bus "+" and bus "-" at 2.5 volts. Termination is the part of the circuitry required to complete the voltage divider network and also provide some electromagnetic protection for the CCD bus. Terminations in all CCD applications have approximately 120 ohms resistance.