Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
CHRYSLER Collision Detection Bus System
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), instrument cluster, Remote Keyless Entry (RKE) module and Sentry Key Immobilizer Module (SKIM). Powertrain Control Module (PCM) and Transmission Control Module (TCM) are not part of body control system, but use CCD bus to communicate.
Coded information identifies message and its importance. When multiple messages attempt to access CCD bus at once, code assigns priority ranking.
CCD bus system uses 2 twisted wires and are called bus "+" (positive) and bus "-" (negative). Both wires carry approximately 2.5 volts. Network consists of some modules with "bias" and some with "termination".
Bias is part of voltage divider network that places both bus "+" and bus "-" at 2.5 volts. Termination is part of circuitry required to complete voltage divider network and also provide some electromagnetic protection for CCD bus. Terminations in all CCD applications have approximately 120 ohms resistance.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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