P2C59

Code

Generic P — Powertrain

Cylinder 4 Fuel Injector B Offset Learning At Max Limit

Brand: Generic

Type: P — Powertrain

Views: UK: 13 EN: 34 RU: 16

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Clogged, leaking, or mechanically degraded fuel injector (Cylinder 4, injector B)
Open, shorted or high-resistance wiring/connector to the injector or driver
Faulty injector driver or PCM output for that injector
Low or high fuel rail pressure or fuel supply issues altering injector flow
Excessive air leak, low compression, or mechanical engine problem at cylinder 4
Contaminated fuel or internal injector deposits preventing proper flow

Symptoms

Check Engine Light (MIL) illumination
Rough idle or vibration, especially at idle
Cylinder-specific misfire or reduced power under load
High or asymmetric long-term fuel trim values
Increased fuel consumption or poor driveability
Difficulty starting or uneven acceleration

What to check

Read DTCs and freeze frame; note conditions (rpm, load, temp, fuel pressure)
Monitor per-cylinder short-term and long-term fuel trims and misfire counts
Perform a recorded capture of injector waveform with a lab scope
Measure injector resistance at the connector and compare to spec
Backprobe injector supply and driver signal for voltage/pulse width while cranking/running
Check fuel rail pressure and regulator operation under load

Signal parameters

Injector DC resistance (typical ranges): low-impedance injectors ~2-5 Ω, high-impedance ~10-18 Ω — use OEM spec
Injector pulse width at idle: commonly ~2–4 ms (varies by engine/load) — compare to other cylinders
Injector drive voltage: supply rail typically battery voltage (~12 V) when energized; driver pulls to ground or uses saturating driver
Expected fuel rail pressure: port-injected systems commonly ~40–60 psi; direct injection much higher — use OEM spec
Desired per-cylinder learned offset value: within small positive/negative range; a value at the stored maximum or minimum flag triggers the code

Diagnostic algorithm

Capture/record freeze frame and live data: note engine speed, load, temp, fuel pressure, short/long term trims, and misfire counts for Cylinder 4.
Clear codes, perform a drive/idle cycle with data logging to confirm reproducibility and to capture adaptive values as learning attempts occur.
Visually inspect injector connector, wiring harness, and nearby components for chafing, corrosion, or oil contamination; repair any issues.
Measure injector coil resistance at the connector and compare to OEM; if out of range, replace injector.
Using a lab scope, capture the injector primary waveform and supply voltage while running; look for missing pulses, abnormal rise/fall, or low drive current.
Perform an injector balance or cylinder cutout test: disable Cylinder 4 injector and note change in RPM/trim. A small change vs other cylinders suggests flow issue.
Swap the suspect injector with another cylinder’s injector and clear codes. If the fault or symptoms move to the other cylinder, replace the injector.
Check fuel rail pressure and regulator function under static and dynamic conditions; repair fuel supply issues if out of spec.
Perform compression and/or leak-down test on Cylinder 4 to exclude mechanical problems that mimic injector flow defects.
If electrical and mechanical tests pass, consider PCM/driver diagnostic (firmware, connector to PCM) and consult manufacturer-specific service info; replace PCM only when supported by evidence.
After repairs, clear codes and perform re-learn procedure if required by manufacturer. Verify the learned offset returns to within normal range.

Likely causes

Injector electrical fault (open/short/high resistance) or poor connector
Injector hydraulically out of spec (clogged, stuck, leaking)
Fuel pressure out of specification (low rail pressure)
Cylinder-specific mechanical issue (low compression or valve leak)
PCM/driver hardware fault or corrupted adaptive data

Fault status

⚠️ Status

Cylinder 4, Fuel Injector B offset learning reached maximum allowed correction. PCM has stored an adaptive limit condition for that injector; MIL may be illuminated and readiness may be affected until fault is resolved.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours