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. P029B means the correction for cylinder 1 is at its lower limit: the module keeps taking fuel away from this cylinder and still cannot even it out – a sign that it receives too much fuel, for example from a dripping injector. 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 1 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- Check engine light on
- Rough idle, vibration
- Higher consumption, smoke or fuel smell
Most likely causes
- Injector of cylinder 1 dripping or leaking
- Injector with excessive flow (worn seat or needle)
- Wrong injector correction code after replacement
- Injector circuit short (extended activation)
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 P029B means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 2: Fuel injection
- 9B: Specific fault in that system
Frequently asked questions
Can I keep driving with code P029B?
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 P029B?
The most common causes are: injector of cylinder 1 dripping or leaking; injector with excessive flow (worn seat or needle); wrong injector correction code after replacement.
Related codes
- P029ACylinder 1 - Fuel Trim at Max Limit
- P029CCylinder 1 - Injector Restricted
- P029DCylinder 1 - Injector Leaking
- P0172System Too Rich Bank 1
- P0263Cylinder 1 Contribution/Balance
- P02CCCylinder 1 Fuel Injector A Offset Learning At Min 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.