P2B08: Cylinder 1 opening feedback fails during catalyst warm-up

P2B08 is the cold-start cylinder 1 injection-pulse performance monitor in the reviewed GM strategy. More precisely, the row requires catalyst-warm-up mode: the cold-start label is not a substitute for confirming that operating state.

The controller looks for actual movement evidence

The ECM uses voltage-flux feedback caused by injector pintle or armature motion. It measures across the injector enable and command wires and calculates an opening-magnitude metric. An undetectable opening or failure of the calibrated missing-pulse comparison indicates that a commanded pulse may not have been delivered as intended.

This separates an injection command from its observed response. It does not directly measure spray pattern or prove a specific mechanical sticking mechanism.

A warm engine test can miss the relevant window

Catalyst warm-up must be enabled, small-pulse general diagnostic enable must be true, and fuel-pulse voltage-feedback data must be ready. The source lists 50–100 samples at a cylinder-event rate.

A later test after warm-up ends does not reproduce those conditions, even if the same cylinder is still being fueled. Preserve the warm-up status and eligible feedback when reviewing a startup event. The general cylinder 1 pulse code P2B00 lacks this additional warm-up condition in its listed row.

Verification should confirm the expected opening signature during an eligible catalyst-warm-up evaluation. Use the applicable professional injector procedure; the source supplies no manual energizing instructions or mandatory replacement. The documented response is Type B, two trips.

Source and applicability

This description is limited to the stated monitor; vehicle, engine and calibration matching remain necessary. GM diagnostic table, PDF page 671.