Powertrain, generic · Fuel and air metering

P01AA Alternative Fuel Tank Temperature Sensor Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Connector or wiring of the tank temperature sensor open, corroded or chafed
Sensor faulty
Gas module, CAN link or engine module

Symptoms

  • Stored fault code (warning light depending on system)
  • Gas level display wrong
  • Gas operation blocked, switch to petrol

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–3,000
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

alternative fuel tank temperature sensorsensor wiring

Related codes

P01ABP01ACP01ADP01AEP019E

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov, patents.google.com.