Bosch Mini Split P4 Error Code

What P4 means

P4 means an inverter compressor drive error on Bosch Climate 5000 systems - the drive's detection circuit saw abnormal feedback (communication, voltage, or compressor rotation-speed signals). Stop using the system: repeated restarts against a drive fault can worsen compressor or IPM damage. One safe reset is allowed; if P4 returns, this is a technician-only fault (wiring, IPM, fan/ventilation, compressor, or outdoor PCB).

First checks before service

This page currently documents the safe reset triage. If the code returns, use the linked source manual or a qualified technician for code-specific diagnosis.

1. 1. One-time fault event (power disturbance or transient sensor reading) common DIY

   Check: Power-cycle at the breaker/disconnect (or unplug for CPAP), restore, and run the system while watching for the code.

   Fix: If the code does not return after a full run cycle, the fault was transient — monitor, no repair needed.

2. 2. Fault persists after a clean reset occasional pro only

   Check: If the code returns immediately or every session, note the conditions (startup, heating, after rain).

   Fix: A persisting code points at the component the manual assigns to this code — that repair is technician territory.