P2B0A stands for missed cold-start pulses on cylinder 3. For the GM 1.2 L LIH with its three cylinders it is the highest cold-start cylinder code, since that engine's 2025 table stops at P2B0A. The same table defines the cold-start window through the summary code P2B95: catalyst below 550 °C, coolant up to 66 °C, 250–3,000 rpm and less than 20 s after start, ending after 500 engine cycles at most – a very short test. Cylinder codes are Type B and decide after 50 to 100 samples. GM bulletin PIP5746 and service update A202310450 (2020–2021 Encore GX, 2021 Trailblazer) both list P2B0A; the cure is ECM reprogramming. Four-cylinder GM engines use the code for their cylinder 3 too. The warm-engine twin is P2B02.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Cylinder 3 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- Lamp on, code stored only after a cold start
- Engine runs normally once warm
Most likely causes
- ECM software anomaly on the GM 1.2 L LIH (service update A202310450)
- Cylinder 3 injector reacting too slowly when cold
- Injector 3 connector with poor contact
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
- It affects emissions.
What each character of P2B0A means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- B: Subsystem depends on the code range
- 0A: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2B0A?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P2B0A?
The most common causes are: eCM software anomaly on the GM 1.2 L LIH (service update A202310450); cylinder 3 injector reacting too slowly when cold; injector 3 connector with poor contact.
Related codes
- P2B02Cylinder 3 Injection Pulse Performance
- P2B09Cold Start Cylinder 2 Injection Pulse Performance
- P2B0BCold Start Cylinder 4 Injection Pulse Performance
- P2B95Cold Start Injection Pulse Performance
- P0203Cylinder 3 Injector A Circuit/Open
- P0303Cylinder 3 Misfire Detected
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 25OBDG03A
- static.nhtsa.gov: MC 10179653 9999
- static.nhtsa.gov: MC 10181656 9999
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.