Fisher & Paykel Dishwasher Error Code U4

The U4 code appears on one tub of a Fisher & Paykel double-drawer dishwasher when the other tub is experiencing an F9 fault. It is a lockout notification, not an independent fault in the tub displaying it. The tub showing U4 cannot operate until the F9 condition on the adjacent tub is resolved. No repairs should be performed on the U4 tub until the F9 fault is addressed first.

The tub displaying U4 is locked out and will not operate while the F9 fault exists on the adjacent tub. The U4 tub itself is not in a hazardous condition, but neither tub should be considered fully functional until the underlying F9 fault is diagnosed and repaired. Avoid repeated reset attempts and address the F9 fault directly.

The cost to resolve a U4 error depends entirely on what is causing the F9 fault on the adjacent tub. Repair costs can range from low-cost fixes like clearing a drain blockage to higher costs if components such as an inlet valve, drain pump, or wash motor need replacement. Parts and labor for those types of repairs typically range from $100 to $400 or more depending on the specific fault and local service rates.

To fix the U4 error, you must diagnose and repair the F9 fault on the other tub in your double dishwasher. The U4 tub itself does not require repair. Once the F9 fault is corrected, the U4 code should clear on its own. Do not attempt to replace the controller on the tub showing U4, as this will not resolve the issue.

A simple reset will not permanently clear the U4 error because the code is caused by an active F9 fault on the paired tub. Even if the display clears temporarily after a reset, the U4 code will return as long as the F9 condition remains unresolved. The only way to permanently clear U4 is to diagnose and fix the F9 fault on the other tub.