P2A47 Alternative Fuel Tank C Pressure Sensor Range/Performance

P2A47 is not about broken wires: the tank C sensor delivers a voltage inside its window, yet the pressure it reports cannot be true. Plausible tests are a value that stays flat while the engine draws gas from tank C, one that does not rise during filling, or a clear gap to tanks A and B after a long rest, since cylinders on a common fill manifold settle to similar pressure. For scale, the bulletin SMB-169 that New Flyer issued for CNG buses expects the high-pressure gauge to read somewhere from 200 psi to 3,600 psi after refuelling. The cause can also be mechanical, such as a tank C valve that never opens (P2A27) or a closed manual valve. No manufacturer publishes P2A47 or its thresholds; CARB demands rationality monitoring of such inputs. Compare with a calibrated gauge before replacing parts.

Likely causes

Symptoms

• Check engine light
• Gas level shown does not match refuelling or consumption
• Shorter driving range on gas

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.