What Does P02AB Mean?
The ECM has detected that the individual fuel trim correction for cylinder 5 has reached its minimum limit, meaning the system is subtracting as much fuel as possible from that cylinder but is still detecting an overly rich condition. This indicates cylinder 5 is receiving too much fuel relative to what the engine management system expects. The driver may notice rough idle, black smoke from the exhaust, poor fuel economy, and a fuel smell.
Common Causes
35%
Leaking cylinder 5 fuel injector allowing excess fuel into the combustion chamber when the injector should be closed or delivering less
20%
Faulty injector driver circuit or ECM holding the cylinder 5 injector open longer than commanded
20%
Carbon buildup on the cylinder 5 intake valve (GDI engines) causing poor fuel atomization and incomplete combustion
15%
Low compression on cylinder 5 causing incomplete combustion and raw fuel passing into the exhaust stream
10%
Contaminated or degraded engine oil diluted with fuel affecting the O2 sensor readings for that bank
Diagnostic Steps
1
Review live data for cylinder 5 individual fuel trim — confirm it is at or near the maximum negative correction limit (typically -25% to -30%) confirming the ECM is pulling as much fuel as it can.
2
Perform a relative compression test via cranking RPM analysis to verify cylinder 5 has adequate compression compared to other cylinders — a weak cylinder can appear rich due to poor combustion efficiency.
3
Remove and inspect the cylinder 5 spark plug for heavy black carbon fouling or wet fuel deposits, which confirm excess fuel is entering the combustion chamber.
4
With the fuel rail removed, apply regulated fuel pressure to the rail and observe the cylinder 5 injector tip for any dripping — specification is typically no more than 1 drop per minute.
5
Check the cylinder 5 injector wiring for short circuits to ground or power using a multimeter, and verify the 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 5 has reached its minimum limit, meaning the system is subtracting as much fuel as possible from that cylinder but is still detecting an overly rich condition. This indicates cylinder 5 is receiving too much fuel relative to ...
The most common cause of P02AB (Cylinder 5 - Fuel Trim at Min Limit) is: Leaking cylinder 5 fuel injector allowing excess fuel into the combustion chamber when the injector should be closed or delivering less
Typical repair costs for P02AB range from $150 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven short distances but should be repaired promptly. Running excessively rich on one cylinder washes oil from the cylinder walls, accelerates catalytic converter degradation, and in severe cases poses a fire risk from raw fuel in the exhaust system.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02AB to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
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