Powertrain, generic (extended)

P2B04 Cylinder 5 Injection Pulse Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P2B04 extends the warm-running missed-pulse check to cylinder 5, so it only matters on engines with five or more cylinders. No manufacturer documents P2B04 publicly as a monitor of its own. Among GM's 2025 V8 documents it turns up solely inside code lists attached to common calibration maps; the main entries there are the cold-start codes P2B08–P2B0F, while warm small-pulse faults of each cylinder go to GM's own offset-learning codes (P10AB/P10AC for cylinder 5). Where it is used, the idea follows the CARB rule that output parts need a functional check: the controller verifies the injector really opened on command. Which physical cylinder carries number 5 depends on the maker's numbering scheme, so check the engine's layout before pulling parts. Cold-start faults here are P2B0C.

Likely causes

Cylinder 5 injector sticking or opening too slowly

Chafed or high-resistance wiring to injector 5

Calibration error in the engine software

Symptoms

Engine warning lamp on
Rough running or misfire on cylinder 5 (P0305)

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€100–1,000

Time0.5–5 h

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

Parts involved

fuel injector cylinder 5injector wiringengine control module

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