What Does P02B7 Mean?
The ECM has detected that the individual fuel trim correction for cylinder 8 has reached its minimum limit. The system is subtracting the maximum possible fuel from cylinder 8 but still detects a rich condition. Cylinder 8 is receiving significantly more fuel than it should, and the ECM cannot compensate further. The driver may notice rough idle, black smoke, poor economy, and strong fuel odor.
Common Causes
35%
Leaking cylinder 8 fuel injector allowing excess fuel into the combustion chamber when the injector should be closed
20%
Faulty injector driver circuit or ECM holding the cylinder 8 injector energized longer than commanded
20%
Carbon buildup on cylinder 8 intake valve (GDI engines) causing poor atomization and incomplete combustion
15%
Low compression on cylinder 8 causing incomplete combustion and raw fuel in the exhaust
10%
Contaminated engine oil diluted with fuel affecting bank-level O2 sensor readings
Diagnostic Steps
1
Review live data for cylinder 8 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 8 has adequate compression compared to other cylinders.
3
Remove and inspect the cylinder 8 spark plug for heavy black carbon fouling or wet fuel deposits confirming excess fuel.
4
With the fuel rail removed, apply regulated fuel pressure and observe the cylinder 8 injector tip for dripping — no more than 1 drop per minute.
5
Check the cylinder 8 injector wiring for short circuits, and verify injector resistance matches specifications (typically 11-17 ohms).
Estimated Repair Cost
$150 - $500
Parts + labor, varies by vehicle and location
The ECM has detected that the individual fuel trim correction for cylinder 8 has reached its minimum limit. The system is subtracting the maximum possible fuel from cylinder 8 but still detects a rich condition. Cylinder 8 is receiving significantly more fuel than it should, and the ECM cannot compe...
The most common cause of P02B7 (Cylinder 8 - Fuel Trim at Min Limit) is: Leaking cylinder 8 fuel injector allowing excess fuel into the combustion chamber when the injector should be closed
Typical repair costs for P02B7 range from $150 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Can be driven short distances but repair promptly. An excessively rich cylinder 8 washes oil from the cylinder walls, damages the catalytic converter with unburned fuel, 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 P02B7 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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