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. P02AD means the module detects fuel entering cylinder 5 outside the injection pulse – the injector is leaking or dripping. A BMW patent identifies such a leak by the fact that it persists with the injector switched off. A leaking diesel injector can dilute the oil or damage the piston, so act promptly. 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?Drive as little as possible and go to a repair shop. If you smell fuel or the engine is shaking badly, do not keep driving.
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
- Smoke, fuel smell, knocking
Most likely causes
- Nozzle seat or needle of the cylinder 5 injector leaking
- Deposits keeping the needle from closing fully
- Rail pressure too high
- Wrong or wrongly coded injector
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 P02AD means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 2: Fuel injection
- AD: Specific fault in that system
Frequently asked questions
Can I keep driving with code P02AD?
Drive as little as possible and go to a repair shop. If you smell fuel or the engine is shaking badly, do not keep driving.
What causes code P02AD?
The most common causes are: nozzle seat or needle of the cylinder 5 injector leaking; deposits keeping the needle from closing fully; rail pressure too high.
Related codes
- P02AACylinder 5 - Fuel Trim at Max Limit
- P02ABCylinder 5 - Fuel Trim at Min Limit
- P02ACCylinder 5 - Injector Restricted
- P0275Cylinder 5 Contribution/Balance
- P02D4Cylinder 5 Fuel Injector A Offset Learning At Min Limit
- P0172System Too Rich Bank 1
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.