P2A4A Alternative Fuel Tank C Pressure Sensor Circuit Intermittent/Erratic

Unlike P2A48 or P2A49, which describe a signal stuck out of range, P2A4A covers a tank C pressure value that flickers: brief spikes, gaps or steps that no gas cylinder could produce, since pressure in a large tank changes only slowly. Vibration is the usual trigger, acting on a connector with weak pin tension, a cable clip that has let go, or water creeping past a seal near the back of the vehicle, where tank C often sits. A sensor failing internally is possible but rarer. Because the defect often vanishes in the workshop, freeze-frame data and a road test with live readings help. No manufacturer documents P2A4A; it mirrors P2A45 for tank B and P01A2 for tank A, and CARB covers such erratic inputs under its component rules.

Likely causes

Symptoms

• Check engine light appearing occasionally
• Gas gauge jumps while driving
• No noticeable effect between dropouts

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.