Powertrain, generic (extended)

P2B08 Cold Start Cylinder 1 Injection Pulse Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2B08 is the cold-start version of the cylinder 1 pulse check. While the catalyst is being heated, many direct-injection engines split each injection into two or three small pulses, and CARB requires for 20/50/100 % of model years 2026/2027/2028 that missing split or multiple pulses be detected during the cold-start strategy. CARB also wants faults found in that phase stored under their own codes, which is why P2B08 exists beside P2B00. GM used it earlier: its tables flag cylinder 1 when the opening signature is missing during catalyst warm-up, Type B. For the 1.2 L LIH in the 2020 Encore GX and 2021 Trailblazer, GM bulletin PIP5746 calls it a software anomaly appearing only on cold starts; verify after an overnight soak.

Likely causes

Cold-start software anomaly (GM 1.2 L LIH, fixed by ECM reprogramming)
Cylinder 1 injector sluggish when cold, missing the short split pulses
Contact fault in injector 1 wiring that shows mainly when cold

Symptoms

  • Warning lamp, often with the engine running normally once warm
  • Possibly slightly rough running in the first seconds after a cold start
  • Code returns only after a long standstill, not on warm restarts

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–900
Time0.3–4 h

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

Parts involved

fuel injector cylinder 1injector wiringengine control module

Related codes

P2B00P2B09P2B95P050DP0201P0301

References: law.cornell.edu, gsi.ext.gm.com, static.nhtsa.gov.