P01AB Alternative Fuel Tank Temperature Sensor Range/Performance

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. P01AB is the plausibility fault: the signal is valid but does not fit – for example compared with ambient temperature after standstill or with the pressure change while refuelling. 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

Symptoms

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

Repair estimate

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

Parts involved

Related codes

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