Mitsubishi 3000GT / Dodge Stealth TCM — Troubleshooting Guide

Mitsubishi 3000GT / Dodge Stealth TCM — Troubleshooting Guide

Important: Use this guide if you reinstalled your repaired Mitsubishi 3000GT / Dodge Stealth TCM and the problem is still happening.
Important: Please do not open/disassemble the TCM or attempt internal repairs.

• Step 1: Confirm the exact symptom
  • Erratic/harsh shifting
  • Transmission not shifting
  • Limp mode/stuck in gear
  • Intermittent shift issue
  • Codes returning after repair
• Step 2: Check battery and charging voltage
  • Low voltage can cause false TCM faults and harsh/erratic shifting.
  • Confirm battery terminals are clean/tight and charging voltage is stable.
• Step 3: Check TCM/ECU/IGN fuses
  • Check related fuses with a meter or test light, not just visually.
  • If a fuse is blown again after replacement, inspect for a short before continuing.
• Step 4: Inspect TCM connector and pins
  • Make sure the TCM connector is fully seated.
  • Look for corrosion on the pins, bent pins, pushed-back terminals, moisture, or loose fit.
• Step 5: Verify TCM powers and grounds
  • Confirm the TCM has proper ignition power, constant power if equipped, and clean ground.
  • Poor ground can cause intermittent shifting, no communication, or repeat codes.
• Step 6: Inspect transmission harness and solenoid wiring
  • Check wiring from the TCM to the transmission for rubbing, oil contamination, broken wires, or loose connectors.
  • Solenoid/harness faults can mimic a bad TCM.
• Step 7: Check transmission sensors and range switch
  • Verify vehicle speed sensor, throttle/TPS signal, and range/neutral safety switch signals.
  • Bad sensor input can cause harsh shifts, wrong shift timing, or no shifting.
• Step 8: Check fluid level and mechanical condition
  • Low/burnt/contaminated fluid can cause slipping, harsh shifting, or no shift.
  • Internal transmission issues can return the same symptoms even with a repaired TCM.
• Step 9: Pull and compare codes after road test
  • Clear codes, road test, then scan again.
  • Codes that return immediately usually point to wiring, solenoid, sensor, power, or ground issues.
• Step 10: If issue continues
  • Have a shop perform voltage-drop testing on TCM power/grounds and pin-to-pin harness testing between the TCM and transmission.