OBD
P04DB
Crankcase Ventilation System Disconnected
What it means
P04DB means Crankcase Ventilation System Disconnected.
Check these first
- A disconnected breather hose
- A loose breather hose connection
- A cracked breather hose
- A failed crankcase pressure sensor
What to do next
- Inspect the breather hose and its connections
- Reconnect or replace any loose or cracked breather hose
- Check the crankcase pressure sensor signal
- Replace the crankcase pressure sensor if it reads wrong after the hose is fixed
- Clear the code and retest
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Updated
Generic SAE J2012 definition. Last updated 2026-10-10.