P029B code meaning
Cylinder 1 - Fuel Trim at Min Limit
Powertrain system Generic code P02xx codes Check engine light
What P029B means
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 gasoline 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.
P029B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor1 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P029B
- Check engine light on
- Rough idle, vibration
- Higher consumption, smoke or fuel smell
Common causes of P029B
- Most likelyInjector of cylinder 1 dripping or leaking
- PossibleInjector with excessive flow (worn seat or needle)
- Less likelyWrong injector correction code after replacement
- Less likelyInjector circuit short (extended activation)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector cylinder 1Crankshaft position sensorEngine control module
What each part of P029B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 2 | Area: fuel and air metering (injector circuit). |
| 9B | The exact fault in that area. |
What to do next
- Note P029B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P029B
What does P029B mean?
P029B means "Cylinder 1 - Fuel Trim at Min Limit". 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 gasoline engines a cylinder-selective mixture control does the same. It is a generic code, so it means the same on every make.
Is it safe to drive with P029B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P029B fail an emissions test?
Yes, it can. P029B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P029B to fix?
Difficulty: medium. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P029B clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.