What Does P02A7 Mean?
The ECM has detected that the individual cylinder fuel trim for cylinder 4 has reached its minimum limit (maximum lean correction). The ECM is removing as much fuel as possible from cylinder 4, but the air/fuel mixture is still too rich. This indicates a persistent over-fueling condition on cylinder 4. Symptoms include rough idle, black exhaust smoke, fuel odor, a carbon-fouled spark plug on cylinder 4, and increased fuel consumption.
Common Causes
35%
Leaking cylinder 4 fuel injector allowing fuel to drip when the injector is commanded closed
20%
Cylinder 4 ignition failure (degraded coil or fouled spark plug) causing incomplete combustion
20%
Carbon buildup on cylinder 4 intake valve disrupting fuel atomization (port-injection engines)
15%
Wrong-specification injector on cylinder 4 with a higher flow rate than other cylinders
10%
Low compression on cylinder 4 resulting in poor combustion and a rich exhaust signature
Diagnostic Steps
1
Monitor cylinder 4 individual fuel trim; confirm it is at or near the maximum negative correction limit (typically -25% to -30%).
2
Perform a fuel injector leak-down test: with the engine off and fuel pressurized, remove the cylinder 4 spark plug and watch for fuel dripping into the bore.
3
Remove and compare the cylinder 4 spark plug to other cylinders; heavy black, wet fouling indicates over-fueling on that specific cylinder.
4
Test ignition coil #4 with a spark tester to verify consistent, strong spark output; also measure primary and secondary coil resistance against specification.
5
Measure cylinder 4 compression (dry and wet); compare to other cylinders. Wet test improvement over 15% suggests ring wear as the cause of poor combustion.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The ECM has detected that the individual cylinder fuel trim for cylinder 4 has reached its minimum limit (maximum lean correction). The ECM is removing as much fuel as possible from cylinder 4, but the air/fuel mixture is still too rich. This indicates a persistent over-fueling condition on cylinder...
The most common cause of P02A7 (Cylinder 4 - Fuel Trim at Min Limit) is: Leaking cylinder 4 fuel injector allowing fuel to drip when the injector is commanded closed
Typical repair costs for P02A7 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Short-distance driving is acceptable. The rich condition on cylinder 4 fouls spark plugs, washes cylinder wall oil, and contaminates the catalytic converter. Prolonged driving can cause permanent catalytic converter damage and oil dilution in the crankcase.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02A7 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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