Leaking or sticking fuel injector on cylinder 2, delivering too much or too little fuel; Vacuum leak at the intake runner or intake manifold gasket serving cylinder 2; Faulty ignition coil, spark plug, or plug boot causing incomplete combustion on cylinder 2; Mechanical fault such as low compression, a worn cam lobe, or a bad valve seat on cylinder 2; Contaminated or restricted fuel injector screen reducing fuel delivery to cylinder 2; Engine coolant temperature or mass airflow sensor error skewing fuel trim globally and pushing cylinder 2 to its limit; Exhaust leak before the oxygen sensor or a lazy upstream oxygen sensor causing false trim corrections

DTC codes / P02xx · Fuel and air metering (injector circuits) / P029E

P029ECylinder 2 - Fuel Trim at Max Limit

Q: What does code P029E mean?

Cylinder 2 - Fuel Trim at Max Limit. P029E means the engine computer has reached the maximum authority it is allowed to add or subtract fuel on cylinder 2 while trying to keep that cylinder's combustion at the target air-fuel ratio. The powertrain control module (PCM) is reporting that the cylinder 2 fuel trim correction has hit its calibrated limit, so it can no longer compensate for the imbalance it is seeing.

P029E means the engine computer has reached the maximum authority it is allowed to add or subtract fuel on cylinder 2 while trying to keep that cylinder's combustion at the target air-fuel ratio. The powertrain control module (PCM) is reporting that the cylinder 2 fuel trim correction has hit its calibrated limit, so it can no longer compensate for the imbalance it is seeing.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other symptoms besides the warning light
Rough idle or a noticeable shake that is worse when the engine is cold
Misfire-like shudder or hesitation under light acceleration
Reduced fuel economy because the computer is adding maximum fuel to one cylinder
A faint fuel or exhaust smell if the cylinder is running rich at the trim limit
Possible slight loss of power or uneven running at steady cruise

Common causes, most likely first

Leaking or sticking fuel injector on cylinder 2, delivering too much or too little fuel
Vacuum leak at the intake runner or intake manifold gasket serving cylinder 2
Faulty ignition coil, spark plug, or plug boot causing incomplete combustion on cylinder 2
Mechanical fault such as low compression, a worn cam lobe, or a bad valve seat on cylinder 2
Contaminated or restricted fuel injector screen reducing fuel delivery to cylinder 2
Engine coolant temperature or mass airflow sensor error skewing fuel trim globally and pushing cylinder 2 to its limit
Exhaust leak before the oxygen sensor or a lazy upstream oxygen sensor causing false trim corrections

How to diagnose and fix it

Scan all modules and record freeze-frame data, then check for related misfire and fuel trim codes before touching any parts
Inspect the intake tract and vacuum lines around cylinder 2 for cracks, loose clamps, and leaking gaskets using a smoke machine
Swap the cylinder 2 ignition coil and spark plug with a neighbouring cylinder and see whether the misfire or trim fault follows
Perform a compression test and, if needed, a cylinder leak-down test on cylinder 2 to rule out mechanical causes
Check fuel injector operation with a noid light or injector balance test, and inspect the injector connector and wiring
Verify fuel pressure and inspect the mass airflow and coolant temperature sensor readings against expected values
Repair the confirmed fault, clear the codes, and road-test through several drive cycles to confirm fuel trim returns within normal range

Cylinder 2 fuel trim limit traps to avoid

A P029E can be set by a problem that is not actually on cylinder 2, because a global vacuum leak or a skewed mass airflow sensor reading can push one cylinder's trim to its limit first.
Technicians often replace the cylinder 2 injector immediately, but a leaking intake gasket at that runner produces the same maxed-out trim and is far cheaper to fix.
The code does not always mean the engine is running rich; a maxed-out positive fuel trim means the computer is adding fuel because it thinks cylinder 2 is lean, which can come from a vacuum leak or low fuel pressure.
A failing ignition coil on cylinder 2 can send unburned oxygen into the exhaust, and the oxygen sensor then reports a false lean condition that drives fuel trim to its limit.
After the repair, fuel trim must be rechecked at idle and at cruise, because a fault that only appears under load will not show up in a stationary idle test.

Can I keep driving with P029E?

You can usually drive the vehicle to a workshop, but avoid heavy acceleration, towing, and long trips until the fault is diagnosed. Continued driving with a maxed-out fuel trim on one cylinder can overheat the catalytic converter and cause expensive damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.