Class 2 Serial Data Line

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Class 2 Serial Data Line
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The class 2 serial data line on this vehicle is a star configuration. The following modules communicate on the class 2 serial data line:

  • The body control module (BCM)
  • The digital radio receiver
  • The driver door module (DDM)
  • The electronic brake control module (EBCM)
  • The front passenger door module (FPDM)
  • The HVAC control module
  • The inflatable restraint sensing and diagnostic module (SDM)
  • The instrument panel cluster (IPC)
  • The memory seat module (MSM)
  • The powertrain control module (PCM)
  • The radio
  • The radio amplifier
  • The rear seat audio (RSA) controller
  • The rear seat entertainment (RSE) assembly w/U42
  • The rear wheel steering control module
  • The remote playback device-CD player w/U1S
  • The transfer case shift control module
  • The transmission control module (TCM) w/Allison Transmission
  • The theft deterrent control module
  • The vehicle communication interface module (VCIM) w/UE1

The class 2 serial data line allows a scan tool to communicate with these modules for testing purposes, checking for DTCs, and to activate/enable/disable functions. These class 2 serial data circuits are bussed together via splice packs and a data link connector (DLC):

  • SP205
  • SP206
  • SP207
  • DLC-connects the scan tool to the class 2 serial data circuits.

Refer to Data Link Communications Component ViewsΒ Β  for an illustrated view of the splice pack locations.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.