P2BF1

Code

Generic P — Powertrain

Fuel Control System B Too Rich Bank 1

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 98 RU: 21

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Page language: EN

Causes

Leaking or stuck-open fuel injector(s) on bank 1
High fuel rail/line pressure or failed fuel pressure regulator
Incorrect MAF/MAP/airflow sensor readings (contamination or failure)
Faulty or slow upstream oxygen/air–fuel sensor or wiring issue
Excessive evaporative purge (stuck-open purge valve) or fuel vapor intrusion
ECM or sensor wiring short to voltage or ground, or poor connector/circuit integrity

Symptoms

Poor fuel economy (higher-than-normal fuel consumption)
Black exhaust smoke or strong fuel smell from tailpipe
Rough idle, hesitation or drivability issues under load
Possible illuminated Check Engine Light with P2BF1 stored
High hydrocarbon (HC) emissions on tailpipe or failed emissions test

What to check

Connect a scan tool and record live data: short-term (STFT) and long-term fuel trims (LTFT) for bank 1 and bank 2, upstream O2 voltages/wideband lambda and fuel rail pressure
Review freeze-frame/test-run data when the code set (engine load, RPM, temp, fuel trim values)
Visually inspect wiring and connectors for bank 1 injectors, O2 sensors, MAF/MAP and fuel pressure sensor for damage or corrosion
Perform a fuel pressure test at idle and under load to compare with manufacturer spec
Perform injector balance/flow/leak testing or remove/inspect suspect injector(s) for leakage
Check operation of the EVAP purge solenoid (actuate and observe leakage/flow)

Signal parameters

Short-term fuel trim (STFT) bank 1: large negative values (example: -10% to -30%) indicate commanded fuel reduction due to rich condition
Long-term fuel trim (LTFT) bank 1: sustained negative values (e.g.
Upstream O2 sensor (narrowband): voltage held high (> ~0.6–0.8 V) or very slow switching; wideband lambda
Fuel rail pressure: higher than spec or unstable pressure under idle/load
Injector pulse width: longer than expected for measured load (may indicate over-fueling)
MAF frequency/voltage: lower than expected for given RPM/load (could cause ECU to add fuel)

Diagnostic algorithm

Step 1 — Scan and document data: read freeze-frame and monitor STFT/LTFT, upstream O2 voltages, MAF/MAP, fuel rail pressure and coolant temperature while reproducing condition.
Step 2 — Check for simple causes: visually inspect wiring/connectors for damage or corrosion on bank 1 (injectors and sensors). Repair connector issues and clear codes to retest.
Step 3 — Fuel pressure: measure static and dynamic fuel rail pressure; compare to spec. If high, inspect/replace fuel pressure regulator or test fuel pressure regulator vacuum line (if applicable).
Step 4 — Injector test: perform a fuel injector balance or leak test. Replace or rebuild any injector that leaks or flows excessively. If uncertain, swap suspect injector with same-bank injector and see if the symptom/code follows.
Step 5 — Air measurement sensors: test/clean MAF and verify MAP; compare airflow readings to expected values. Replace sensor if readings are inconsistent or out of range.
Step 6 — O2/UEGO sensor: monitor upstream oxygen sensor response time and voltage/wideband lambda accuracy. If sensor is slow or stuck rich, verify wiring and replace sensor if needed.
Step 7 — EVAP purge: verify purge valve operation (actuation and flow). A stuck-open purge can introduce excess fuel vapor — replace if faulty.
Step 8 — Electrical: check injector driver circuits for shorts to voltage, shorted MOSFETs in ECM or wiring faults that could hold injectors open.
Step 9 — After repairs: clear codes and perform a verified test drive with live data logging to confirm STFT/LTFT and O2 behavior return to expected ranges and code does not reappear.

Likely causes

Leaking injector(s) on bank 1
Fuel pressure regulator diaphragm leak or stuck high-pressure condition
Contaminated/failed MAF causing low airflow signal and overfuelling
Stuck-open EVAP purge solenoid introducing excess fuel vapors
Upstream O2/UEGO sensor stuck high or reporting rich, preventing proper fuel trim correction
Shorted injector driver circuit forcing injector(s) open