SPN 2003 Code Explained and Troubleshooting

SPN 2003 is a diagnostic trouble code for bad connection between ECM and TCM.

ECM, TCM wiring harness


  1. Safety first: Before starting any work on your vehicle, disconnect the negative terminal of the battery to prevent any electrical hazards or damage to the ECM/TCM.
  2. Locate the ECM and TCM: Refer to your vehicle’s service manual to find the location of the ECM and TCM. They are usually located in the engine compartment or under the dashboard.
  3. Visually inspect the wiring harness: Look for any signs of damage, fraying, or corrosion in the wiring harness connected to the ECM and TCM. Also, check for any loose or damaged connectors.
  4. Check for continuity and resistance: Use a multimeter to test the continuity and resistance of the wiring harness. Refer to the service manual for the proper pinout and resistance values of each wire. If any wires have no continuity or incorrect resistance, they will need to be repaired or replaced.
  5. Inspect grounds: Make sure all grounding points are clean, tight, and free of corrosion. Poor grounding can cause various issues with the ECM and TCM.
  6. Check for short circuits and open circuits: Use the multimeter to check for short circuits between wires and open circuits in the wiring harness. Repair or replace any damaged sections of the wiring harness as needed.
  7. Inspect the connectors: Check the connectors for any bent or damaged pins, corrosion, or loose connections. Repair or replace damaged connectors as necessary.
  8. Reconnect the battery and clear codes: Reconnect the negative battery terminal and use a diagnostic tool to clear any stored trouble codes related to the ECM and TCM.