Code
P2B1B
Generic
P — Powertrain
Cylinder 6 Injection Pulse Offset Exceeded Learning Limit
Views:
UK: 22
EN: 31
RU: 21
AI status
Completed
Completed
100%
Causes
- Faulty or sticking fuel injector on cylinder 6
- Open, shorted or corroded injector wiring or connector for cylinder 6
- Faulty injector driver circuit in the engine control module (ECM)
- Low or unstable fuel rail pressure or failing fuel pump/regulator
- Mechanical problem in cylinder 6 (low compression, valve or piston issues)
- Intake or vacuum leak affecting only cylinder 6 or local air/fuel balance
Symptoms
- Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
- Rough idle or vibration, often felt as a cylinder-specific misfire
- Reduced engine power, hesitation or stumble under load
- Increased fuel consumption or black exhaust smoke (rich condition)
- Stored misfire or injector-related codes (e.g., P0306, P0206) may also appear
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Observe live data: injector pulse width for all cylinders, short/long term fuel trims, misfire counters and O2 sensor response
- Check fuel rail pressure and regulator operation under key-on and running conditions
- Perform visual inspection of injector 6 connector, wiring harness and ground connections
- Measure injector 6 electrical resistance and compare to manufacturer specification
- Backprobe injector 6 while cranking/running to verify injector drive signal and voltage
Signal parameters
- Injector pulse width (ms) — compare cylinder 6 to other cylinders under equivalent conditions
- Injector electrical resistance (Ω) — compare to specification for that vehicle's injector type
- Fuel rail pressure (psi or bar) — steady and within manufacturer spec during cranking and running
- Short-term and long-term fuel trim (%) — look for cylinder-specific imbalance
- Misfire count for cylinder 6 (events/min or per second) from scan tool
- ECM learned offset value for injector corrections (ms or %), and the learn-limit threshold
Diagnostic algorithm
- Connect scan tool, record current DTCs and freeze-frame. Note RPM, load, fuel trims, injector pulse widths and misfire counters.
- Visually inspect injector 6 connector and wiring for damage, corrosion or loose terminals. Repair as necessary.
- Check fuel pressure and regulator operation; verify adequate and stable rail pressure under load.
- Measure injector 6 resistance and compare to spec. Backprobe the injector driver during cranking/running to confirm proper command voltage and ground.
- Compare injector pulse width and injector behavior of cylinder 6 to other cylinders. Look for significantly higher pulse width or learning offset.
- Perform a compression or leak-down test on cylinder 6 to rule out mechanical causes that would demand additional fuel.
- If electrical tests are inconclusive, swap injector 6 with a known-good injector from a different cylinder and clear codes. If the fault follows the injector, replace the injector.
- If the fault remains on cylinder 6 after swapping injectors, inspect and repair wiring/ECM driver for that injector circuit. Check cam/crank sensors and timing if timing-related symptoms present.
- After repairs or injector replacement, clear codes and perform a road test to allow the ECM to relearn injector offsets. Confirm the code does not return.
- If suspect ECM driver or firmware, consult manufacturer resources for reprogramming or ECM replacement procedures.
Likely causes
- Dirty, partially clogged, or mechanically sticking injector on cylinder 6
- Wiring or connector damage/corrosion at injector 6
- Fuel pressure low or fluctuating causing abnormal injector pulse compensation
- Cylinder 6 mechanical condition (low compression or leakage) requiring more fuel
- Injector driver fault in ECM (less common than wiring/injector problems)
Fault status
Status
Injector adaptation for cylinder 6 exceeded allowable offset during learning. MIL set; further inspection of injector, circuit, fuel delivery or cylinder condition required.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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