How to check the DTCs on your Cummins without using a code reader.

  1. Put the key in the ignition with doors closed.
  2. Cycle the key THREE times from the OFF position to the RUN position without cranking the engine. Leave in the RUN position on the THIRD cycle. Note: The RUN position is TWO clicks while the ACCESSORY position is only ONE click.

    Example: KEY IN (OFF) – RUN – OFF – RUN – OFF – RUN

  3. If there are any DTCs present, they will be displayed one at a time on the odometer
  4. When all codes have been displayed, or there are no codes, the odometer will read “DONE