P2A79

Q: Can I keep driving with this code?

The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.

Alternative Fuel Hydraulic Pump Pressure Sensor Circuit Intermittent/Erratic

High severity

The alternative fuel hydraulic pump pressure sensor signal drops out or jumps intermittently. Loose connector or noisy ground.

Common causes

Sensor connector not seated
One of the most commonly reported causes for this code — check this first.
high
Typical part cost: $220-1100
Noisy ground reference
A plausible cause — test and verify before replacing parts.
medium
Typical part cost: $220-1100
See all causes + fix costs
Create a free Wrenchify account to unlock the rest for P2A79.
Unlock causes
Free forever · No credit card

First things to check

1Confirm the code with a scan tool and check for additional related codes.
2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.

Get the full step-by-step diagnosis

Create a free Wrenchify account to unlock the rest for P2A79.

Unlock diagnosis

Free forever · No credit card

Related codes

See related trouble codes

Create a free Wrenchify account to unlock the rest for P2A79.

Unlock related codes

Free forever · No credit card

Frequently asked questions

What does P2A79 mean?

P2A79 means "Alternative Fuel Hydraulic Pump Pressure Sensor Circuit Intermittent/Erratic". It is a generic OBD-II code that points to a fault in the auxiliary emission controls.

What are the most common causes of P2A79?

sensor connector not seated; noisy ground reference; connector with intermittent contact under vibration — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.

Can I keep driving with this code?

This code can put the vehicle into limp or reduced-power mode. Avoid extended driving and have the vehicle diagnosed promptly. Use the Wrenchify app for a full diagnosis specific to your vehicle.

Get the full P2A79 diagnosis for your vehicle

Year, make, model + step-by-step repair help — free plan included.

Diagnose P2A79