P2BB2 code meaning
Alternative Fuel Tank Empty
What P2BB2 means
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 gasoline. 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 gasoline 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.
P2BB2 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2BB2
- Engine runs on gasoline only, gas mode cannot be selected
- Gas gauge shows empty or low-level warning
Common causes of P2BB2
- Most likelyGas tank actually used up to its reserve
- PossibleTank pressure or level sensor reading too low
- Less likelyTank shutoff valve closed or not opening
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Alt fuel tankAlt fuel level sensor
What each part of P2BB2 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| B | Area: hybrid propulsion. |
| B2 | The exact fault in that area. |
What to do next
- Note P2BB2 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2BB2
What does P2BB2 mean?
P2BB2 means "Alternative Fuel Tank Empty". P2BB2 reports that the tank for the second fuel, mostly CNG or LPG, has been drawn down to its usable minimum. It is a generic code, so it means the same on every make.
Is it safe to drive with P2BB2?
P2BB2 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P2BB2 fail an emissions test?
P2BB2 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P2BB2 to fix?
Difficulty: easy. A typical repair takes 0 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P2BB2 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.