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.

High severity. Can I keep driving?If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.

Symptoms

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

Most likely causes

Connector pins at the tank C sensor with weak contact
Water ingress at a connector seal
Harness clip loose, cable rubbing

What to check, in order

Start with the simplest. You can tick off each step.

If you smell gas, shut off the supply, ventilate and do not start the engine
Gently move the wiring with the engine running and watch whether the reading changes.
Read the codes with a compatible scanner
Check the connectors and wiring of the component indicated
Leave any work on the gas circuit to an authorized shop

Good to know

Repair difficulty: hard
It affects emissions.

What each character of P2A4A means

P: Powertrain: engine and transmission
2: Generic code: same on every make
A: Hybrid or air and fuel
4A: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2A4A?

If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.

What causes code P2A4A?

The most common causes are: connector pins at the tank C sensor with weak contact; water ingress at a connector seal; harness clip loose, cable rubbing.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.