P01A1 code meaning
Alternative Fuel Tank A Pressure Sensor Circuit High
Powertrain system Generic code P01xx codes Check engine light
What P01A1 means
These codes only apply to vehicles that run on a gaseous alternative fuel – compressed natural gas (CNG) or LPG – either as bi-fuel models alongside gasoline (for example GM's 2015–2016 Impala Bi-Fuel or 2013–2016 Silverado/Sierra 2500HD) or as dedicated gas engines. CNG is stored at up to about 250 bar (3600 psi); a regulator reduces it to a few bar for the gas rail and injectors. The tank pressure sensor A sits at or in the regulator; together with the tank temperature it gives the gas level, and it decides whether gas operation is possible. P01A1 means the signal voltage is above its upper limit – typically an open sensor ground or a signal wire shorted to 5 V or battery voltage. Typical reaction: gas operation is blocked and a bi-fuel vehicle switches to gasoline. No manufacturer document naming exactly this code was found; GM's bulletins only state that faults are reported like on gasoline models. The description rests on CARB, which treats such vehicles like gasoline engines for model years 2004–2018, and on the documented system design.
P01A1 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P01A1
- Check engine light on
- Gas level gauge wrong, jumping or showing empty
- Gas operation blocked or automatic switch to gasoline
- Dedicated gas engines: limp mode or starting problems possible
Common causes of P01A1
- Most likelySensor ground wire open
- PossibleSignal wire shorted to 5 V reference or battery voltage
- PossibleTank pressure sensor faulty internally
- Less likelyControl module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Alternative fuel tank pressure sensorGas pressure regulatorSensor wiring
What each part of P01A1 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| A1 | The exact fault in that area. |
What to do next
- Note P01A1 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 P01A1
What does P01A1 mean?
P01A1 means "Alternative Fuel Tank A Pressure Sensor Circuit High". These codes only apply to vehicles that run on a gaseous alternative fuel – compressed natural gas (CNG) or LPG – either as bi-fuel models alongside gasoline (for example GM's 2015–2016 Impala Bi-Fuel or 2013–2016 Silverado/Sierra 2500HD) or as dedicated gas engines. It is a generic code, so it means the same on every make.
Is it safe to drive with P01A1?
Drive gently and only to a workshop. With P01A1 the car can go into limp mode (reduced power) to protect itself.
Will P01A1 fail an emissions test?
Yes, it can. P01A1 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 P01A1 to fix?
Difficulty: hard. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will P01A1 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.