P01A2: Alternative Fuel Tank A Pressure Sensor Circuit Intermittent/Erratic

What does P01A2 mean?

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 petrol (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. P01A2 covers brief dropouts or jumps in the signal – usually a loose contact or a harness chafing along the gas line or underbody. Typical reaction: gas operation is blocked and a bi-fuel vehicle switches to petrol. No manufacturer document naming exactly this code was found; GM's bulletins only state that faults are reported like on petrol models. The description rests on CARB, which treats such vehicles like petrol engines for model years 2004–2018, and on the documented system design.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Gas level gauge wrong, jumping or showing empty
• Gas operation blocked or automatic switch to petrol
• Dedicated gas engines: limp mode or starting problems possible

Common causes

• High Loose contact or corrosion at the connector, wire broken by vibration
• Medium Harness chafed along the gas line or underbody
• Medium Sensor unstable internally
• Low Poor ground point or interference

Likelihood is a general estimate across vehicles; your make and model may differ.