P1AFB

Code

Generic P — Powertrain

Fuel Injector Control Circuit Performance - Bank B

Brand: Generic

Type: P — Powertrain

Views: UK: 7 EN: 8 RU: 8

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Page language: EN

Causes

Open or short in injector wiring harness (Bank B)
Corroded or loose injector connector(s)
Failed fuel injector(s) on Bank B
Faulty PCM / injector driver transistor
Poor battery/charging system voltage or weak ground
Blown fuse or bad fuel injector relay

Symptoms

Malfunction Indicator Lamp (MIL) on / stored P1AFB code
Rough idle or misfire(s) affecting cylinders on Bank B
Reduced engine power, hesitation under load
Poor fuel economy and elevated emissions
Difficulty starting or extended crank time
Sometimes fuel odor if injector leaking

What to check

Read DTCs and freeze frame / live data to confirm problem and affected cylinders
Visually inspect injector harness, connectors, and PCM connector for corrosion, bent pins, or damage
Check battery voltage and chassis/engine grounds before testing
Verify related fuses and fuel injector relay
Compare injector command data and any available current/feedback data for Bank B vs Bank A
Listen for injector operation with a stethoscope (qualitative) — compare bank-to-bank

Signal parameters

Injector resistance: vehicle-specific. Typical ranges — low-impedance injectors ~2–5 Ω, high-impedance ~10–18 Ω. Always use OEM spec.
Injector command: pulse-width modulation from PCM. Typical pulse widths idle ~1–5 ms, under load up to ~8–12 ms depending on engine and RPM.
Connector voltages: one terminal usually battery voltage (~12 V key ON) and the other is switched to ground by PCM when commanded (measure with back-probe)
Oscilloscope waveform: square pulses on the driver line (or pull-to-ground pattern). Look for missing pulses, distorted edges, or abnormal voltage levels.
Current-sensing systems: look for expected current spikes during injection; absence or erratic current indicates wiring/injector/driver issue.

Diagnostic algorithm

Retrieve all stored codes and freeze-frame data. Note which cylinders are on Bank B.
Verify battery voltage >= 12.4 V with key ON and during cranking. Poor voltage can cause false faults.
Perform visual inspection of harness, connectors, and PCM pins for Bank B. Repair any obvious damage before further testing.
Check related fuses and injector power feed/relay. Verify constant feed to injector rail/connectors with key ON.
Measure DC resistance of each injector on Bank B (engine off, harness disconnected) and compare to specs and to bank A.
Back-probe injector connector while cranking/engine running: verify feed voltage on the power side and that PCM-side switches to ground when commanded. Use oscilloscope if available to examine waveform.
If a multi-injector fault affects all Bank B injectors, check for a common power feed or ground fault, and inspect shared splice points.
Swap a suspected injector from Bank B to an identical position on Bank A (if accessible) and see if the code or symptom follows the injector (if safe and practical).
Check continuity from injector connector to PCM driver pin for opens/shorts. Repair wiring as needed.
If wiring and injectors test good and problem persists, test or replace PCM/injector driver per manufacturer procedure.
After repair, clear codes and perform a road test or monitor live data to ensure the fault does not return.

Likely causes

Wiring/connector problem (pin corrosion, broken wire, poor ground) affecting all or multiple injectors on Bank B
One or more injectors on Bank B electrically shorted or open
Failed injector driver inside the PCM
Low battery/poor charging voltage resulting in abnormal injector drive
Intermittent connection at splice or ECU connector

Fault status

⚠️ Status

Fuel Injector Control Circuit Performance — Bank B. PCM reports injector control or feedback performance outside expected range for Bank B; inspect injectors, wiring/connectors, and PCM driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1–3 hours