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P code powertrain High severity

P2603 Coolant Pump "A" Control Circuit High

The OBD2 code P2603 indicates that there is a high voltage signal detected in the control circuit of the coolant pump "A," which may suggest a malfunction in the pump or its control system

Definition

The OBD2 code P2603 indicates that there is a high voltage signal detected in the control circuit of the coolant pump "A," which may suggest a malfunction in the pump or its control system

Common causes

  • Faulty coolant pump
  • Open or shorted wiring in the control circuit
  • Corroded or damaged connectors
  • Faulty engine control module (ECM)
  • Poor ground connection
  • Blown fuse in the coolant pump circuit
  • Incorrectly installed or damaged coolant pump relay

Common misdiagnoses

  • Faulty coolant pump
  • Wiring issues or shorts in the circuit
  • Faulty engine control module (ECM)
  • Incorrect coolant level or condition
  • Thermostat malfunction
  • Faulty temperature sensor
  • Issues with the cooling system (e.g., leaks)
  • Electrical connector problems
  • Software issues in the ECM
  • Other related sensor failures

Troubleshooting steps

  1. 1. Check the Code

    Use an OBD-II scanner to confirm that the P2603 code is present. Clear the code and see if it returns after a short drive

  2. 2. Visual Inspection

  3. 3. Inspect the wiring and connectors associated with the coolant pump. Look for any signs of damage, corrosion, or loose connections

  4. 4. Check the coolant pump itself for any physical damage or leaks

  5. 5. Test the Coolant Pump

  6. 6. If accessible, test the coolant pump for proper operation. You can do this by applying direct battery voltage to the pump to see if it runs

  7. 7. If the pump does not operate when powered directly, it may need to be replaced

  8. 8. Check the Control Circuit

  9. 9. Use a multimeter to check the voltage at the coolant pump connector. You should see a voltage reading when the engine is running and the pump is commanded on

  10. 10. If the voltage is too high or too low, trace the wiring back to the engine control module (ECM) to identify any breaks or shorts

  11. 11. Inspect the ECM

  12. 12. If the wiring and pump are functioning correctly, the issue may lie with the ECM. Check for any software updates or recalls related to the ECM

  13. 13. If necessary, perform a bench test of the ECM or consult a professional for further diagnosis

  14. 14. Check for Other Codes

    Look for any other related trouble codes that may provide additional context for the issue. Sometimes, multiple codes can point to a common problem

  15. 15. Test the Relay and Fuses

  16. 16. If the coolant pump is controlled by a relay, check the relay for proper operation. Swap it with a similar relay in the fuse box to see if the problem resolves

  17. 17. Inspect the fuses related to the coolant pump circuit to ensure they are not blown

  18. 18. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the P2603 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations

  19. 19. Professional Diagnosis

    If the issue persists after performing these steps, it may be best to consult a professional mechanic or technician who has access to advanced diagnostic tools and equipment. By following these steps, you should be able to identify and resolve the issue related to the P2603 code