P2A6B: Alternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Circuit Low

P2A6B is stored when the signal voltage of the regulator inlet pressure sensor drops below its valid band. With a typical three-wire transducer (5 V feed, signal, ground) that means a signal lead shorted to ground, a lost 5 V reference or a failed sensor element. A low voltage would read as an almost empty cylinder, so a bi-fuel vehicle may refuse gas mode or show an empty gauge with a full tank; Ford's 2003 bi-fuel CNG logic drove the gauge to empty whenever the sensor built into its regulator failed. GM uses the same reading on the Impala together with tank temperature to work out the fill level. No maker publishes P2A6B directly. Measure feed and signal at the plug with the key on before condemning the sensor.

Symptoms

• Check engine light on
• Gas gauge shows empty although the tank is full
• Gas mode refused, bi-fuel vehicle runs on petrol

Most likely causes

• Signal wire chafed through and shorted to ground
• 5 V reference open or pulled down by another sensor on the same feed
• Inlet pressure transducer internally shorted

What to check, in order

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

1. If you smell gas, shut off the supply, ventilate and do not start the engine
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Read the codes with a compatible scanner
4. Check the connectors and wiring of the component indicated
5. Leave any work on the gas circuit to an authorized shop

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P2A6B means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• A: Hybrid or air and fuel
• 6B: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2A6B?

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 P2A6B?

The most common causes are: signal wire chafed through and shorted to ground; 5 V reference open or pulled down by another sensor on the same feed; inlet pressure transducer internally shorted.

Related codes

• P2A69Alternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Circuit
• P2A6AAlternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Range/Performance
• P2A6CAlternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Circuit High
• P2A6DAlternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Circuit Intermittent/Erratic
• P01A0Alternative Fuel Tank A Pressure Sensor Circuit Low

Sources

• law.cornell.edu: 13 CCR 1968.2
• static.nhtsa.gov: INRD PE08063 33504P
• static.nhtsa.gov: MC 10114282 9999

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.