P2BB2Alternative Fuel Tank Empty
- Generic OBD-II code · Powertrain
- How the car detects it
- P2BB2 reports that the tank for the second fuel, mostly CNG or LPG, has been drawn down to its usable minimum. It is a status message rather than a component fault: a bi-fuel vehicle simply goes back to petrol. GM's bulletins for its bi-fuel models show the logic: the ECM derives the gas level from the tank pressure sensor, the 2013 Silverado and Sierra 2500HD gauge reads empty at roughly 500 psi and the 2015 Impala at about 400 psi, and when the gas is used up the engine changes to petrol on its own; GM's documents name no DTC for this step. No maker documents P2BB2 openly. If it appears with a full tank, suspect the tank pressure or level sensor (P019E, P01AF) or a closed tank shutoff valve (P224C). CARB treats such engines as alternate-fueled vehicles.
- What you may notice
- Engine runs on petrol only, gas mode cannot be selected
- Gas gauge shows empty or low-level warning
- Likely causes
- LikelyGas tank actually used up to its reserve
- PossibleTank pressure or level sensor reading too low
- RareTank shutoff valve closed or not opening
- Repair
- Easy · Often possible to do yourself.Typical cost: €0 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.