What Does P02A6 Mean?
The ECM has detected that the individual cylinder fuel trim for cylinder 4 has reached its maximum enrichment limit. The ECM is adding as much fuel as possible to cylinder 4, but the air/fuel ratio remains too lean. This indicates a localized lean condition on cylinder 4 from an air leak, restricted injector, or exhaust leak at that cylinder. The driver may notice rough idle, a cylinder 4 misfire, or hesitation under acceleration.
Common Causes
35%
Vacuum leak at the cylinder 4 intake port, runner gasket, or nearby intake manifold seal
30%
Partially clogged or restricted cylinder 4 fuel injector reducing fuel delivery
15%
Exhaust leak at the cylinder 4 exhaust port or manifold gasket causing a false lean oxygen sensor reading
12%
Low fuel pressure from a degraded pump or restricted filter affecting cylinder 4 fuel delivery
8%
Cylinder 4 compression issue from worn rings or valve sealing problem causing lean exhaust
Diagnostic Steps
1
Monitor cylinder 4 individual fuel trim via the scan tool; confirm it is at or near the maximum positive enrichment limit (typically +25% to +30%).
2
Perform a smoke test on the intake manifold, focusing on the cylinder 4 intake runner and port area; observe for smoke escaping from gasket surfaces, cracks, or vacuum connections.
3
Test cylinder 4 injector delivery using an injector balance test; compare the RPM drop when disabling cylinder 4 vs. all other cylinders.
4
Measure fuel system pressure at the rail during idle and snap throttle; it should remain within specification and not drop under demand.
5
Inspect the exhaust manifold at cylinder 4 for cracks or gasket failure; at cold startup, listen for exhaust ticking and feel for pulses at the gasket flange.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
The ECM has detected that the individual cylinder fuel trim for cylinder 4 has reached its maximum enrichment limit. The ECM is adding as much fuel as possible to cylinder 4, but the air/fuel ratio remains too lean. This indicates a localized lean condition on cylinder 4 from an air leak, restricted...
The most common cause of P02A6 (Cylinder 4 - Fuel Trim at Max Limit) is: Vacuum leak at the cylinder 4 intake port, runner gasket, or nearby intake manifold seal
Typical repair costs for P02A6 range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven short distances at reduced load. A lean condition on cylinder 4 causes elevated exhaust temperature that can damage the catalytic converter. Avoid towing or heavy load situations until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02A6 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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