What Does P02AA Mean?
The ECM has detected that the individual fuel trim correction for cylinder 5 has reached its maximum enrichment limit, meaning the system is adding as much extra fuel as it can to that cylinder but is still detecting a lean condition. This indicates a significant air/fuel imbalance on cylinder 5 where insufficient fuel is reaching the combustion chamber. The driver may notice a misfire, rough idle, hesitation, or reduced power.
Common Causes
30%
Clogged or partially restricted cylinder 5 fuel injector reducing fuel delivery below the ECM's compensation range
25%
Vacuum leak at the cylinder 5 intake runner gasket or port allowing unmetered air into that cylinder
20%
Faulty cylinder 5 injector electrical circuit causing reduced injector pulse width or intermittent operation
15%
Low fuel pressure at the rail causing inadequate fuel delivery to cylinder 5, especially under load
10%
Exhaust leak near the cylinder 5 port introducing false air readings to the O2 sensor
Diagnostic Steps
1
Review live data for cylinder 5 individual fuel trim — confirm it is at or near the maximum positive correction limit (typically +25% to +30%) indicating the ECM cannot add enough fuel.
2
Perform a smoke test on the intake manifold to check for vacuum leaks at the cylinder 5 intake runner, gasket surfaces, and any connected vacuum hoses.
3
Compare injector flow rates using an injector balance test or by monitoring the rpm drop when disabling each injector individually — cylinder 5 should show a similar drop to the others.
4
Check fuel rail pressure under key-on engine-off (typically 55-62 PSI) and at idle (should hold within 5 PSI of spec), then verify it maintains pressure under load with a snap throttle test.
5
Inspect the cylinder 5 injector connector for corrosion, backed-out pins, or damaged wiring, and measure injector resistance (typically 11-17 ohms for high-impedance injectors).
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 maximum enrichment limit, meaning the system is adding as much extra fuel as it can to that cylinder but is still detecting a lean condition. This indicates a significant air/fuel imbalance on cylinder 5 whe...
The most common cause of P02AA (Cylinder 5 - Fuel Trim at Max Limit) is: Clogged or partially restricted cylinder 5 fuel injector reducing fuel delivery below the ECM's compensation range
Typical repair costs for P02AA range from $150 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Driving is possible but not recommended for extended periods. A maxed-out lean fuel trim means cylinder 5 is running lean, which can cause elevated combustion temperatures, potential catalytic converter damage from misfires, and in extreme cases, piston or valve damage from detonation.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02AA to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
