A faulty or contaminated fuel injector on cylinder 7 that cannot deliver the expected pulse response; Carbon buildup or mechanical wear on the cylinder 7 injector tip altering its flow characteristics; A weak or failing ignition coil or spark plug on cylinder 7 causing an unstable combustion signal during the learn routine; Low fuel pressure or a restricted fuel supply that prevents the ECM from completing the offset learn; A wiring fault or poor connection at the cylinder 7 injector connector or the ECM harness; An internal ECM fault or corrupted adaptive memory that prevents the learned offset from being stored; A vacuum leak or intake leak near cylinder 7 that skews the air-fuel mixture during the learn cycle

DTC codes / P2Bxx · Hybrid propulsion / P2B1C

P2B1CCylinder 7 Injection Pulse Offset Not Learned

Q: What does code P2B1C mean?

Cylinder 7 Injection Pulse Offset Not Learned. P2B1C means the engine control module (ECM) has not been able to learn the injection pulse offset for cylinder 7, which is the small fuel-delivery correction the ECM applies to that cylinder's injector to keep all cylinders balanced. The ECM commands a learn routine during specific operating conditions and stores this code when the expected correction value cannot be stored or verified.

P2B1C means the engine control module (ECM) has not been able to learn the injection pulse offset for cylinder 7, which is the small fuel-delivery correction the ECM applies to that cylinder's injector to keep all cylinders balanced. The ECM commands a learn routine during specific operating conditions and stores this code when the expected correction value cannot be stored or verified.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A slight rough idle or vibration that is more noticeable when the engine is cold
Intermittent misfire sensation or hesitation under light acceleration
Slightly elevated fuel consumption if the ECM defaults to a rich correction
Poorer throttle response or a subtle loss of power on some vehicles
No drivability change at all in many cases, with the code found only during a scan

Common causes, most likely first

A faulty or contaminated fuel injector on cylinder 7 that cannot deliver the expected pulse response
Carbon buildup or mechanical wear on the cylinder 7 injector tip altering its flow characteristics
A weak or failing ignition coil or spark plug on cylinder 7 causing an unstable combustion signal during the learn routine
Low fuel pressure or a restricted fuel supply that prevents the ECM from completing the offset learn
A wiring fault or poor connection at the cylinder 7 injector connector or the ECM harness
An internal ECM fault or corrupted adaptive memory that prevents the learned offset from being stored
A vacuum leak or intake leak near cylinder 7 that skews the air-fuel mixture during the learn cycle

How to diagnose and fix it

Connect a scan tool and record all stored and pending codes, then check freeze-frame data for the conditions when P2B1C set
Inspect the cylinder 7 injector connector and harness for corrosion, chafing, or loose pins, and verify injector resistance if specifications are available
Check fuel pressure and fuel trim values to rule out a supply or mixture problem before condemning the injector
Perform a cylinder contribution or power balance test to compare cylinder 7 against the others
Swap the cylinder 7 ignition coil and spark plug with a neighbouring cylinder to see if the fault follows the component
Run the manufacturer's injector offset learn or adaptation reset procedure with a capable scan tool after any repair
If the learn still fails, replace the cylinder 7 injector and repeat the learn procedure, then clear codes and verify the repair

What the offset learn routine really needs

The ECM only runs the cylinder 7 offset learn under a narrow set of conditions, so a code can set simply because the engine never reached the required temperature or load during short trips.
A perfectly healthy injector can fail the learn if fuel pressure is marginally low or if a small vacuum leak exists near that cylinder, so always verify those basics before replacing parts.
Some vehicles store P2B1C after a battery replacement or ECM reprogramming because the adaptive memory was cleared and the learn cycle has not yet completed.
A misfire code for cylinder 7 may not be stored alongside P2B1C, which leads some technicians to overlook an ignition or compression problem that is disturbing the learn routine.
Clearing the code without completing the offset learn procedure often results in the code returning within a few drive cycles, so the learn must be run after every repair.

Can I keep driving with P2B1C?

The vehicle is generally safe to drive with P2B1C because the ECM falls back to a default injection offset, but avoid heavy towing or sustained high-load driving until the fault is repaired. If a noticeable misfire or rough running develops, have it diagnosed promptly to prevent damage to the catalytic converter.

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.