What Does P02BB Mean?
The ECM has detected that the individual fuel trim correction for cylinder 9 has reached its minimum limit. The system is removing the maximum possible fuel from cylinder 9 but still detects a rich condition. Cylinder 9 is receiving substantially more fuel than commanded, and the ECM cannot compensate further. This applies to engines with 9+ cylinders. The driver may notice rough running, black smoke, and fuel odor.
Common Causes
35%
Leaking cylinder 9 fuel injector allowing excess fuel into the combustion chamber when closed
20%
Faulty injector driver circuit or ECM holding cylinder 9 injector open longer than commanded
20%
Carbon buildup on cylinder 9 intake valve (GDI engines) causing poor atomization and incomplete combustion
15%
Low compression on cylinder 9 causing incomplete combustion and unburned fuel in exhaust
10%
Fuel-contaminated engine oil or failing PCV system affecting O2 sensor readings on that bank
Diagnostic Steps
1
Review live data for cylinder 9 individual fuel trim — confirm it is at or near the maximum negative correction limit (typically -25% to -30%).
2
Perform a relative compression test via cranking RPM analysis to verify cylinder 9 has adequate compression — low compression causes poor combustion that reads as rich.
3
Remove and inspect the cylinder 9 spark plug for heavy black carbon fouling or wet fuel deposits.
4
With the fuel rail removed, apply regulated fuel pressure and observe the cylinder 9 injector tip for dripping — no more than 1 drop per minute.
5
Check the cylinder 9 injector wiring for short circuits and verify injector resistance (typically 11-17 ohms).
Estimated Repair Cost
$200 - $600
Parts + labor, varies by vehicle and location
The ECM has detected that the individual fuel trim correction for cylinder 9 has reached its minimum limit. The system is removing the maximum possible fuel from cylinder 9 but still detects a rich condition. Cylinder 9 is receiving substantially more fuel than commanded, and the ECM cannot compensa...
The most common cause of P02BB (Cylinder 9 - Fuel Trim at Min Limit) is: Leaking cylinder 9 fuel injector allowing excess fuel into the combustion chamber when closed
Typical repair costs for P02BB range from $200 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Can be driven short distances but repair promptly. Persistent rich operation on cylinder 9 washes oil from cylinder walls, damages the catalytic converter, and in severe cases creates a fire risk from raw fuel in the exhaust.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02BB to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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