What does HP POST Code 90B mean?
HP BIOS detected that the cooling fan is not operating and will throttle/shut down to prevent overheating.
Common causes
- Dust-clogged cooling fan
- Failed fan bearing
- Disconnected fan connector
- Fan connector damaged
- Thermal control IC failure
Diagnostic & testing steps
- 1. Listen for fan - if silent during startup, fan is not spinning
- 2. Disassemble laptop and access fan connector
- 3. Clean fan and heatsink fins with compressed air
- 4. Test fan with direct 5V connection
- 5. Replace fan if seized or making grinding noise
Tools required
- Compressed air
- Pentalobe/Phillips screwdriver
- 5V power source for fan test
OEM parts & part numbers
Cooling Fan, Thermal Paste
Part numbers: L14366-001, L78718-001
Safety warning
⚠️ Running laptop without fan will cause immediate thermal damage to CPU. Do not operate without cooling.
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