Faulty or clogged fuel injector for cylinder 7, delivering too little or too much fuel; Vacuum leak at the intake manifold runner or gasket specific to cylinder 7; Worn or fouled spark plug or ignition coil causing incomplete combustion that skews fuel trim; Leaking intake manifold gasket or cracked intake runner affecting only that cylinder; Exhaust leak before the oxygen sensor that corrupts the feedback signal used for trim calculation; Mechanical issue such as low compression or a sticking valve on cylinder 7; Contaminated fuel or a failing fuel pressure regulator affecting delivery to one cylinder

DTC codes / P02xx · Fuel and air metering (injector circuits) / P02B2

P02B2Cylinder 7 - Fuel Trim at Max Limit

Q: What does code P02B2 mean?

Cylinder 7 - Fuel Trim at Max Limit. P02B2 means the engine control module has detected that the fuel trim correction for cylinder 7 has reached its maximum allowed limit, indicating the engine computer can no longer compensate for an excessively lean or rich condition on that specific cylinder. The module monitors crankshaft speed fluctuations and oxygen sensor feedback to isolate the imbalance to cylinder 7, and it sets this code when the long-term fuel trim adjustment for that cylinder stays pegged at the limit for a calibrated period.

P02B2 means the engine control module has detected that the fuel trim correction for cylinder 7 has reached its maximum allowed limit, indicating the engine computer can no longer compensate for an excessively lean or rich condition on that specific cylinder. The module monitors crankshaft speed fluctuations and oxygen sensor feedback to isolate the imbalance to cylinder 7, and it sets this code when the long-term fuel trim adjustment for that cylinder stays pegged at the limit for a calibrated period.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or a noticeable vibration that may be more pronounced when the engine is cold
Slight hesitation or stumble during acceleration, especially under light throttle
Decreased fuel economy as the computer struggles to balance the air-fuel mixture
Occasional misfire sensation or a flashing check engine light under heavy load if the condition worsens

Common causes, most likely first

Faulty or clogged fuel injector for cylinder 7, delivering too little or too much fuel
Vacuum leak at the intake manifold runner or gasket specific to cylinder 7
Worn or fouled spark plug or ignition coil causing incomplete combustion that skews fuel trim
Leaking intake manifold gasket or cracked intake runner affecting only that cylinder
Exhaust leak before the oxygen sensor that corrupts the feedback signal used for trim calculation
Mechanical issue such as low compression or a sticking valve on cylinder 7
Contaminated fuel or a failing fuel pressure regulator affecting delivery to one cylinder

How to diagnose and fix it

Connect a scan tool and record freeze-frame data and long-term fuel trim values for all cylinders to confirm the imbalance is isolated to cylinder 7
Perform a visual inspection of the intake and exhaust systems around cylinder 7 for obvious leaks, cracks, or disconnected hoses
Swap the ignition coil and spark plug from cylinder 7 with a known-good cylinder to see if the misfire or trim imbalance moves
Use a noid light or injector balance test to check the fuel injector pulse and spray pattern for cylinder 7
Run a compression test and cylinder leak-down test on cylinder 7 to rule out mechanical faults
Smoke-test the intake system to locate any vacuum leaks that could affect only that cylinder
If all external causes are ruled out, replace the suspect fuel injector and recheck fuel trim values

Cylinder 7 fuel trim traps to avoid

A vacuum leak at the intake manifold runner for cylinder 7 can mimic a failing injector, so always smoke-test the intake before condemning parts.
This code can be set by a lazy oxygen sensor that responds slowly, causing the computer to overcorrect fuel trim for one cylinder even though the sensor is not dead.
Exhaust leaks upstream of the oxygen sensor can introduce false air and skew fuel trim readings, leading to unnecessary injector replacement.
On engines with variable valve timing, a sticking phaser or solenoid can affect cylinder 7 specifically and set this code without any ignition or fuel fault.
A dirty mass airflow sensor can cause global fuel trim drift that shows up first on the cylinder with the weakest ignition or injector, so check global trims before focusing on cylinder 7 alone.

Can I keep driving with P02B2?

You can usually drive the vehicle short distances at moderate speeds, but avoid heavy acceleration or towing until the fault is diagnosed. Prolonged driving with a maxed-out fuel trim can damage the catalytic converter and worsen engine performance.

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.