P2B08Cold Start Cylinder 1 Injection Pulse Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- 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
- Likely causes
- LikelyCold-start software anomaly (GM 1.2 L LIH, fixed by ECM reprogramming)
- PossibleCylinder 1 injector sluggish when cold, missing the short split pulses
- RareContact fault in injector 1 wiring that shows mainly when cold
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.