2003 Cadillac CTS StandardFACTORY OEM SERVICE PROCEDURE

IMS (Transmission Internal Mode Switch)

Range:Β  Displays Park, Park/Reverse, Reverse, Reverse/Neutral, Neutral, Neutral/Drive 4, Drive 4, Drive 4/Drive 3, Drive 3, Drive 3/Drive 2, Drive 2, Drive 2/Drive 1, Drive 1, Invalid or Open. The IMS Range display represents a decoded status of the four inputs from the IMS. This range includes all possible in-between gear states as well as the detent gear states. The combination of IMS inputs to the PCM are used by the PCM in order to determine what position the manual valve is in at any time.

Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

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.