2021 VW Jetta (5C) instrument cluster would not power up on the bench with APP2 APPRO22 key programmer although the pinout was said to be correct.
The core issue is that only the “crack/programming” connection (e.g. RH850 / MCU adapter board) was used, but the main 12V supply to the cluster (and ignition feed) was never properly provided.
Some MQB/PQ platforms will not light the display on a bare bench unless they receive both permanent battery (Terminal 30) and ignition (Terminal 15), solid grounds, and sometimes CAN wake‑up frames. Therefore the absence of illumination does not always indicate a bad cluster.
Likely causes:
- Missing main 12V (battery) and separate ignition 12V feed; only tool power present.
- Ground not bonded to all required ground pins
- If the car is still dead, you can still read the VIN via OBD, export data, and request firmware repair.
- If VIN/ID can be read, communication layer is alive; lack of backlight alone does not prove failure.
If you want to test whether the instrument is normal, please click here to test the wiring
One more question：
Why don’t connect the system info i need backup system info？
A: The software must enable the 12V output power.
This step requires powering the meter again.
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