How to clear the DTCs (check engine light) on your Cummins without using a code reader.

NOTE: Depending on which flash is on your PCM, there is a chance that this procedure will not work. In that case, it is best to use an OBD-II scanner to clear the codes.

  1. Put the key in the ignition with doors closed.
  2. Cycle the key FIVE times from the OFF position to the RUN position without cranking the engine. Leave in the RUN position on the FIFTH 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 – OFF – RUN – OFF – RUN
  3. This will clear any DTCs that are currently active or stored in the PCM.