P01AA code meaning
Alternative Fuel Tank Temperature Sensor Circuit
Powertrain system Generic code P01xx codes Check engine light
What P01AA means
These codes only apply to vehicles with a gaseous alternative fuel – compressed natural gas (CNG) or LPG – as bi-fuel models alongside gasoline or as dedicated gas engines; on bi-fuel vehicles a fault usually blocks gas operation and the vehicle runs on gasoline. The tank temperature sensor is an NTC thermistor: with CNG there is no float, so the gas level is calculated from tank pressure and tank temperature (GM: full at about 3600 psi at 21 °C, empty at about 400–500 psi). On GM's 2015 Impala Bi-Fuel the sensor is built into the tank and cannot be replaced separately. P01AA is the general circuit fault of this sensor without telling low from high. No manufacturer document using exactly this code was found; the description rests on CARB, which treats such vehicles like gasoline engines for model years 2004–2018, and on the documented system design.
P01AA at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P01AA
- Stored fault code (warning light depending on system)
- Gas level display wrong
- Gas operation blocked, switch to gasoline
Common causes of P01AA
- Most likelyConnector or wiring of the tank temperature sensor open, corroded or chafed
- PossibleSensor faulty
- Less likelyGas module, CAN link or engine module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Alternative fuel tank temperature sensorSensor wiring
What each part of P01AA 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. |
| AA | The exact fault in that area. |
What to do next
- Note P01AA 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 P01AA
What does P01AA mean?
P01AA means "Alternative Fuel Tank Temperature Sensor Circuit". These codes only apply to vehicles with a gaseous alternative fuel – compressed natural gas (CNG) or LPG – as bi-fuel models alongside gasoline or as dedicated gas engines; on bi-fuel vehicles a fault usually blocks gas operation and the vehicle runs on gasoline. It is a generic code, so it means the same on every make.
Is it safe to drive with P01AA?
Drive gently and only to a workshop. With P01AA the car can go into limp mode (reduced power) to protect itself.
Will P01AA fail an emissions test?
Yes, it can. P01AA 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 P01AA to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P01AA 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.