Other Things To Consider
  1. Use the ICD Test Interface module to verify that the debugger is functioning correctly (See ICD Test Interface Module).
  2. There may be a problem programming in general. As a test, switch to Run mode (Run>Run Project) and program the target with the simplest application possible (e.g., a program to blink an LED). If the program will not run, then you know that something is wrong with the target setup.
  3. It is possible that the target device has been damaged in some way (e.g., overcurrent). Development environments are notoriously hostile to components. Consider trying another target device.
  4. Review debugger operation to ensure proper application setup. For more information, see Operation.
  5. Your program speed may be set too high for your circuit. In MPLAB®X IDE, go to File>Project Properties>Program Options>Program Speed and select a slower speed from the drop-down menu. The default is Normal.

6. If the MPLAB X IDE or MPLAB Integrated Programming Environment (IPE) cannot communicate with the MPLAB ICD 4 debugger (LEDs continually alternate between purple and blue), perform the following steps:

How to Force Bootload Mode:


Disconnect the Mini-B USB cable from the debugger.


Perform one of the following two options:

  • If the recommended Microchip 9V power supply (AC002014) is connected to the MPLAB ICD 4, unplug the power supply only from the wall or power strip.
  • If the recommended power supply is not being used, make sure no power is connected to the debugger. Then, insert a small metal screwdriver into the 9V female barrel connector so that it contacts the center pin and the metal tang at the bottom of the jack.


Next, plug the Mini-B USB cable back into the debugger.


As soon as both LEDs flash quickly, immediately unplug the power cable from the debugger or remove the screwdriver (within 1 second). If the LEDs are steady on purple, proceed to the next step. If the LEDs are blue, you did not perform the action fast enough and must repeat the process starting at step a).


Try to reestablish communication with the MPLAB X IDE or MPLAB IPE. If successful, the latest firmware is automatically downloaded and the debugger goes through a built-in self-test. When complete, the LEDs are steady on blue and the debugger is ready for operation.

Refer to Indicator Lights (LEDs) for more information on LED modes and bootloader errors. If the problem persists, contact moc.pihcorcim|etadpu_4DCI#troppuS pihcorciM.

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