P2A42 code meaning
Alternative Fuel Tank B Pressure Sensor Range/Performance
Powertrain system Generic code P2Axx codes Check engine light
What P2A42 means
Unlike its electrical siblings, P2A42 deals with a tank B pressure reading that is electrically valid but makes no sense. Examples: the value does not fall while gas is drawn from tank B, it stays frozen after refuelling, or it differs clearly from the pressure of the other cylinders after a long stop, when all tanks connected to one fill line should settle at about the same level. New Flyer's bulletin SMB-169 for CNG buses gives a sense of the scale: after filling, the high-pressure gauge is expected to show between 200 and 3,600 psi. A tank valve stuck closed (P2A23) or a closed hand valve also starves the reading of change. No manufacturer publishes P2A42 or its limits; CARB requires a rationality check for such inputs. Diagnosis compares the sensor with a mechanical gauge.
P2A42 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor1 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P2A42
- Check engine light
- Gas gauge implausible after refuelling or driving
- Reduced range on gas
Common causes of P2A42
- Most likelyTank B pressure sensor drifting or stuck
- PossibleTank B solenoid stuck closed or manual valve shut
- PossibleContact resistance in the sensor connector shifting the signal
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Alt fuel tank b pressure sensorWiring harnessAfcm
What each part of P2A42 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| A | Area: hybrid propulsion. |
| 42 | The exact fault in that area. |
What to do next
- Note P2A42 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 P2A42
What does P2A42 mean?
P2A42 means "Alternative Fuel Tank B Pressure Sensor Range/Performance". Unlike its electrical siblings, P2A42 deals with a tank B pressure reading that is electrically valid but makes no sense. It is a generic code, so it means the same on every make.
Is it safe to drive with P2A42?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2A42 fail an emissions test?
Yes, it can. P2A42 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2A42 to fix?
Difficulty: hard. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will P2A42 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.