These codes only apply to vehicles with a gaseous alternative fuel – compressed natural gas (CNG) or LPG – as bi-fuel models alongside petrol or as dedicated gas engines; on bi-fuel vehicles a fault usually blocks gas operation and the vehicle runs on petrol. 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 petrol engines for model years 2004–2018, and on the documented system design.
High severity. Can I keep driving?If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.
Symptoms
- Stored fault code (warning light depending on system)
- Gas level display wrong
- Gas operation blocked, switch to petrol
Most likely causes
- Connector or wiring of the tank temperature sensor open, corroded or chafed
- Sensor faulty
- Gas module, CAN link or engine module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P01AA means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- AA: Specific fault in that system
Frequently asked questions
Can I keep driving with code P01AA?
If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.
What causes code P01AA?
The most common causes are: connector or wiring of the tank temperature sensor open, corroded or chafed; sensor faulty; gas module, CAN link or engine module.
Related codes
- P01ABAlternative Fuel Tank Temperature Sensor Range/Performance
- P01ACAlternative Fuel Tank Temperature Sensor Circuit Low
- P01ADAlternative Fuel Tank Temperature Sensor Circuit High
- P01AEAlternative Fuel Tank Temperature Sensor Circuit Intermittent/Erratic
- P019EAlternative Fuel Tank A Pressure Sensor Circuit
Sources
- law.cornell.edu: 13 CCR 1968.2
- static.nhtsa.gov: MC 10114282 9999
- static.nhtsa.gov: MC 10118628 9999
- patents.google.com: US9004050
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.