What Does P02A3 Mean?
The ECM has detected that the individual cylinder fuel trim for cylinder 3 has reached its minimum limit (maximum lean correction). The ECM is removing as much fuel as possible from cylinder 3, but the mixture is still too rich. This indicates an over-fueling condition specific to cylinder 3 that exceeds the adaptive fuel system's correction capability. Symptoms include rough idle, black smoke, fuel odor, and a fouled spark plug on that cylinder.
Common Causes
35%
Leaking cylinder 3 fuel injector allowing fuel to drip into the combustion chamber when commanded closed
20%
Cylinder 3 ignition component failure (weak coil or fouled plug) causing incomplete combustion
20%
Carbon buildup on cylinder 3 intake valve disrupting fuel atomization and causing pooling
15%
Wrong-specification injector installed on cylinder 3 with higher flow rate than other cylinders
10%
Low compression on cylinder 3 causing incomplete burn and rich exhaust
Diagnostic Steps
1
Monitor cylinder 3 individual fuel trim; confirm it is at or near the maximum negative (lean correction) limit, typically -25% to -30%.
2
Perform a fuel injector leak-down test: with the engine off and fuel rail pressurized, remove the cylinder 3 spark plug and observe for fuel dripping over 10-15 minutes.
3
Remove and inspect the cylinder 3 spark plug; heavy black, wet fouling compared to other plugs confirms over-fueling on that cylinder.
4
Test ignition coil #3 secondary output using a spark tester; verify consistent, strong blue spark. Also measure primary coil resistance (typically 0.5-1.5 ohms).
5
Measure cylinder 3 compression and compare to other cylinders; low compression causes poor combustion efficiency. Variation above 15% warrants further investigation.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The ECM has detected that the individual cylinder fuel trim for cylinder 3 has reached its minimum limit (maximum lean correction). The ECM is removing as much fuel as possible from cylinder 3, but the mixture is still too rich. This indicates an over-fueling condition specific to cylinder 3 that ex...
The most common cause of P02A3 (Cylinder 3 - Fuel Trim at Min Limit) is: Leaking cylinder 3 fuel injector allowing fuel to drip into the combustion chamber when commanded closed
Typical repair costs for P02A3 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Driving is possible for short trips. The rich condition on cylinder 3 washes oil from the cylinder wall, fouls the spark plug, and contaminates the catalytic converter substrate. Extended driving risks permanent catalytic converter damage and increased fuel consumption.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02A3 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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