These codes belong to an individual-cylinder fuel correction: a diesel's cylinder balance control measures each cylinder's crankshaft acceleration and adjusts its injection quantity; on petrol engines a cylinder-selective mixture control does the same. CARB requires the system to report when such a correction has used up its range or one cylinder causes an imbalance. P02AA means the correction for cylinder 5 is at its upper limit: the module keeps giving this cylinder more fuel and still cannot even it out – a sign that the cylinder receives too little fuel or builds too little pressure. GM and Ford use other codes for this (P0263 ff, P219A ff); no manufacturer document describing this code with thresholds was found, so the description follows CARB and published patents.
Medium severity. Can I keep driving?You can drive in moderation for a short time. A very lean or very rich mixture can damage the engine or the catalytic converter.
Cylinder 5 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- Check engine light on
- Rough idle, vibration
- Lack of power, possibly misfire
Most likely causes
- Injector of cylinder 5 coked or partly clogged
- Compression loss in this cylinder (valve, rings, leak at injector or glow plug)
- Injector circuit high-resistance or connector
- Petrol: false air at this cylinder's intake (manifold gasket)
- Injector correction code missing or wrong after replacement
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P02AA means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 2: Fuel injection
- AA: Specific fault in that system
Frequently asked questions
Can I keep driving with code P02AA?
You can drive in moderation for a short time. A very lean or very rich mixture can damage the engine or the catalytic converter.
What causes code P02AA?
The most common causes are: injector of cylinder 5 coked or partly clogged; compression loss in this cylinder (valve, rings, leak at injector or glow plug); injector circuit high-resistance or connector.
Related codes
- P02ABCylinder 5 - Fuel Trim at Min Limit
- P02ACCylinder 5 - Injector Restricted
- P02ADCylinder 5 - Injector Leaking
- P0171System Too Lean Bank 1
- P0275Cylinder 5 Contribution/Balance
- P02D5Cylinder 5 Fuel Injector A Offset Learning At Max Limit
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.