Skip to main content
Error code reference
Bosch Heat Pump Error Codes
29 error codes documented with diagnostic procedures.
Have your model number? Get codes specific to your unit.
AtLAmbient temperature limited condition-ambient temperature beyond operating range…C3T3 sensor is not reading correctly in cooling mode.E4Temperature sensor fault (T3, T4, T5, Th, T3L, TF)-shorted or open.E5High/low voltage protection-power supply ≥270V or <172V.E6Outdoor DC fan motor fault.E7T5 sensor (compressor discharge temp sensor) not reading correctly.E9EEPROM IC20 fault-poor contact or improperly installed.F1High pressure protection (same as P1, fault code variant).H0Communication fault in EEPROM IC14 chip.H5Low pressure protection hard lockout-occurs when P2 triggers 5 times in 100 minutes…H8Pressure transducer (PT) fault.L0IPM module protection-control board failed, compressor failed, or abnormal pressure.L1IPM module protection-control board failed, compressor failed, or abnormal pressure.L2IPM module protection-control board failed, compressor failed, or abnormal pressure.L3IPM module protection-control board failed, compressor failed, or abnormal pressure.L4IPM module protection-control board failed, compressor failed, or abnormal pressure.L5IPM module protection-control board failed, compressor failed, or abnormal pressure.L6IPM module protection-control board failed, compressor failed, or abnormal pressure.L7IPM module protection-control board failed, compressor failed, or abnormal pressure.L8IPM module protection-control board failed, compressor failed, or abnormal pressure.L9IPM module protection-control board failed, compressor failed, or abnormal pressure.P0Control board is over-heated due to poor heat dissipation, Tf sensor failure, or wrong…P1High pressure protection.P2Low pressure protection.P3Compressor over current protection.P4High compressor discharge temperature (T5) protection.P5Condenser coil temperature (T3) protection in cooling.P8DC outdoor fan motor protection, typically caused by severe weather (fan running in…PHLow discharge superheat protection.
Get the full diagnostic procedure for any code
Step-by-step tests, expected values, wiring diagram references, and verified part numbers.
Get Started $9.95 3-day pass$29/month for all brands and Max diagnostics, with 70 Max messages a day. Plus applicable tax.