A faulty anode drain valve solenoid or its internal coil, which may be open or shorted.; Damaged, corroded, or disconnected wiring or connector at the valve or along the circuit.; A blown fuse or relay that supplies power to the anode drain valve circuit.; A poor ground connection for the valve or the PCM, causing erratic circuit behavior.; A malfunctioning PCM driver circuit, though this is less common and should be confirmed after other causes are ruled out.; Contamination or mechanical binding inside the valve that prevents proper operation and affects the circuit feedback.; Aftermarket accessories or improper previous repairs that have disturbed the circuit wiring.

DTC codes / U35xx · Network communication / U356A

U356AAnode Drain Valve Control Circuit

Q: What does code U356A mean?

Anode Drain Valve Control Circuit. U356A indicates that the powertrain control module (PCM) has detected an abnormal condition in the electrical circuit that controls the anode drain valve, which is part of the fuel system's evaporative emission control or a similar pressure-management device. The PCM monitors the circuit for expected voltage or current and sets this code when the signal falls outside the manufacturer's specified range, indicating an open, short, or component fault.

U356A indicates that the powertrain control module (PCM) has detected an abnormal condition in the electrical circuit that controls the anode drain valve, which is part of the fuel system's evaporative emission control or a similar pressure-management device. The PCM monitors the circuit for expected voltage or current and sets this code when the signal falls outside the manufacturer's specified range, indicating an open, short, or component fault.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork communication

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) on the dashboard, often with no other noticeable symptoms.
A slight fuel odor may be present if the valve fails to seal properly and allows fuel vapor to escape.
Rough idle or hesitation during acceleration if the valve malfunction affects fuel tank pressure regulation.
Increased evaporative emissions, which may be detected during an emissions inspection.
In some cases, a faint clicking or ticking noise from the valve area may be heard when the ignition is on.
Possible reduction in fuel economy if the valve fault disrupts the fuel system's pressure balance.

Common causes, most likely first

A faulty anode drain valve solenoid or its internal coil, which may be open or shorted.
Damaged, corroded, or disconnected wiring or connector at the valve or along the circuit.
A blown fuse or relay that supplies power to the anode drain valve circuit.
A poor ground connection for the valve or the PCM, causing erratic circuit behavior.
A malfunctioning PCM driver circuit, though this is less common and should be confirmed after other causes are ruled out.
Contamination or mechanical binding inside the valve that prevents proper operation and affects the circuit feedback.
Aftermarket accessories or improper previous repairs that have disturbed the circuit wiring.

How to diagnose and fix it

Use an OBD-II scanner to retrieve all stored codes and freeze-frame data, then clear the code and test-drive to see if it returns.
Visually inspect the anode drain valve, its connector, and the wiring harness for obvious damage, corrosion, or loose pins.
Check the fuse and relay that supply power to the valve circuit, and replace any that are faulty.
Measure the resistance of the valve solenoid with a multimeter and compare it to the manufacturer's specification to check for an open or shorted coil.
Backprobe the valve connector and measure voltage and ground signals while commanding the valve on and off with a scan tool to verify circuit integrity.
If the circuit and valve test good, check for a faulty PCM by verifying the driver signal at the PCM connector; replace or reprogram the PCM only as a last resort.
After repairs, clear the codes and perform a thorough test drive to confirm the code does not return and that all monitors are ready.

Anode Drain Valve Circuit Pitfalls

A common mistake is replacing the anode drain valve without first checking the wiring harness for chafing or corrosion, which can mimic a failed valve.
The code can be set by a momentary glitch in the circuit, so always clear it and verify it is a hard fault before condemning any component.
A weak battery or charging system issue can cause erratic voltage signals that trigger this code, so check battery health and grounds first.
On some vehicles, the anode drain valve is part of the fuel tank pressure sensor assembly, and a fault in that sensor can set a related code that may be misdiagnosed as a valve issue.
Aftermarket alarm or remote start installations often tap into the same wiring harness and can introduce resistance or shorts that set this code.

Can I keep driving with U356A?

You can generally continue driving with this code, but avoid refueling to the brim and monitor for fuel odors or drivability issues. Have the fault diagnosed soon to prevent potential emissions failures or fuel system complications.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.