Powertrain, generic (extended)

P2B18 Cylinder 5 Injection Pulse Offset Not Learned

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P2B18 means injector 5 has no learned offset. No manufacturer documents this exact code. On petrol direct injection GM covers a related idea with codes of its own: in the 2025 V8 table the ECM adds up the opening magnitude and closing time compensation of each injector, both derived from the feedback voltage, and P10AB or P10AC set for cylinder 5 when that sum is below the minimum or above the maximum limit (Type B, 50 to 100 samples). A not-learned status, by contrast, says that no usable value exists yet, for example after a new injector or control unit or after an adaption reset. For diesel engines CARB (f)(4.2.4)(A)(i) requires detection of feedback that does not start in time. The limit-exceeded twin is P2B19.

Likely causes

New injector 5 or control unit without a completed learn

Enabling conditions for the learn not met often enough

Faulty injector 5 wiring preventing a valid measurement

Symptoms

Warning lamp
Rarely noticeable; at most slightly uneven low-load running

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€0–1,500

Time0.3–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel injector cylinder 5engine control module

References: law.cornell.edu, gsi.ext.gm.com.