Symptom:
The head unit screen remains black and fails to power on after performing an MCU firmware update.
Cause:
This issue typically occurs when an incompatible MCU firmware version is flashed to the device. Our systems utilize two distinct MCU versions depending on your vehicle's original system: NBT/EVO and CCC/CIC. Cross-flashing (e.g., installing NBT/EVO firmware on a CIC system) will trigger a safety mechanism, preventing the screen from booting.
Resolution (Emergency Recovery Procedure):
Do not worry, your device is not permanently damaged. You can perform a "manual wake-up" procedure to force the screen to boot, allowing you to flash the correct MCU firmware.
SAFETY WARNING: Ensure your vehicle's ignition is completely turned off before proceeding. Handle exposed wires with care to prevent short circuits.
Instructions:
Disconnect the Power: Remove the screen from the dashboard and unplug the main ISO connector from the back of the unit.
Expose the Wiring: Carefully remove the black insulating tape from the ISO harness to access the individual wires.
Locate the Target Wires: Identify the Yellow wire (Constant 12V Power) and the Blue wire (ACC IN) on the ISO harness.
Strip the Insulation: Use wire strippers or a utility knife to carefully remove a small section of insulation from the middle of both the yellow and blue wires. (Note: Only strip the outer insulation; do NOT cut the wires!)
Bridge the Connection: Temporarily twist the exposed sections of the blue ACC IN wire and the yellow 12V wire together. Be sure to wrap this connection with electrical tape to prevent accidental short circuits against metal components.
Force Boot & Update: Plug the modified ISO harness back into the screen. The unit will now be forced to boot up normally. Once powered on, please install the correct MCU version.
Restore Wiring: After the update is successful, unplug the ISO connector again. Separate the Blue and Yellow wires. Individually wrap the exposed sections of both wires tightly with electrical tape to ensure complete insulation.
Reinstallation: Re-tape the entire ISO harness back to its original factory condition, plug it into the screen, and reinstall the unit into your dashboard. The issue is now resolved.
Further assistance
If the above steps did not resolve your issue, or if you have any other questions, please contact our official customer service team for technical support:
(After-sales email:service@pempcar.com)
