What causes fault code P02F8?

• Most likely: Fuel injector cylinder 4 is clogged or mechanically worn • Likely: Incorrect IMA/ISA injector coding in the ECU • Possible: High resistance in wiring or connectors (oxidation) • Rare: Low fuel rail pressure or contaminated fuel

Powertrain (Engine & Gearbox)Standard EOBD

P02F8 - Cylinder 4 Fuel Injector Offset Learning At Limit

Q: What are the symptoms of fault code P02F8?

• Check engine light (MIL) illuminated • Rough idling or misfires under partial load • Increased fuel consumption • Excessive smoke from exhaust or knocking sounds • Limp home mode (reduced engine power) • Failed emissions test

Q: How do you fix fault code P02F8?

STEP 1: Inspect the connector for injector 4 for oxidation or loose pins. Clean if necessary. STEP 2: Verify that the injector's IMA/ISA classification code matches the value programmed in the ECU using a diagnostic tool. STEP 3: Perform a fuel return flow test (leak-off test) to identify internal mechanical wear. High return flow often triggers offset limit codes. STEP 4: Measure injector resistance (typical range 0.2 - 0.5 Ohms for piezo or 12-14 Ohms for solenoid, verify with service manual). Check wiring harness for continuity. STEP 5: If the injector fails tests, replace it and perform the necessary adaptation/coding in the ECU.

Last updated:1 February 2026

Related:Fuel Injector Cylinder 4, Engine Control Unit (ECU), Common Rail Pressure Sensor, Wiring Harness

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0200

Injector Circuit Malfunction

P0201

Cylinder 1 Injector Circuit Open

P0202

Injector Circuit - Cylinder 2 - Malfunction

P0203

Injector Circuit - Cylinder 3

Technical Description

P02F8 indicates that the Engine Control Unit (ECU) has reached its maximum or minimum limit for adaptive fuel trim compensation (offset learning) for the cylinder 4 fuel injector. The ECU monitors crankshaft acceleration variations to ensure each cylinder contributes equally. When the injector's performance deviates beyond pre-defined limits—due to electrical resistance changes or mechanical wear—the ECU can no longer compensate for the delivery volume, and the DTC is stored. This often relates to the injector's ability to respond to very short injection pulses (IMA/ISA coding).

Possible Causes

Fuel injector cylinder 4 is clogged or mechanically worn

Incorrect IMA/ISA injector coding in the ECU

High resistance in wiring or connectors (oxidation)

Low fuel rail pressure or contaminated fuel

Symptoms

Check engine light (MIL) illuminated

Rough idling or misfires under partial load

Increased fuel consumption

Excessive smoke from exhaust or knocking sounds

Limp home mode (reduced engine power)

Failed emissions test

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P02F8 - Cylinder 4 Fuel Injector Offset Learning At Limit

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P02F8 - Cylinder 4 Fuel Injector Offset Learning At Limit

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