P2A81: Alternative Fuel Pump A Compression Stroke Valve Control Circuit Low

P2A81 is stored when the control circuit of pump A's compression stroke valve sits lower than the commanded state allows. With a low-side driver this mostly points to the control wire touching ground, which can energise the solenoid permanently; with a high-side driver a coil with shorted turns or a grounded feed pulls the output down until its protection trips. A valve held in the fill position keeps oil on the drive side, so the plunger cannot retract and refill, and pump A stays parked at full travel. In Caterpillar's six-element layout the remaining elements may cover part of the demand. No manufacturer publishes P2A81. Disconnect the valve and test the control wire for continuity to chassis ground.

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

Warning lamp on
Pump A stops delivering, power drops at high load

Most likely causes

Control wire of valve A shorted to ground
Shorted turns in the solenoid coil
Water in the valve connector

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
With the connector unplugged, check whether the signal wire is making contact with ground.
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 can trigger limp mode.
It affects emissions.

What each character of P2A81 means

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

Frequently asked questions

Can I keep driving with code P2A81?

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 P2A81?

The most common causes are: control wire of valve A shorted to ground; shorted turns in the solenoid coil; water in the valve connector.

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.