Frigidaire Dishwasher i20 & i21 Error Repair in Port St. Lucie

Quick symptom overview

Frigidaire Gallery and Professional dishwashers display i20 (Drain Timeout / Water Level Not Dropping) or i21 (High Water Level / Overfill Risk) when the analogue pressure switch sensor (5304509705) or its air chamber fails to communicate water depth changes to the main control board.

The electronic water level monitoring system functions as follows: Main control board (154881001 / 5304512726) → 5 VDC reference voltage → pressure switch sensor (5304509705) → sump pressure dome / air tube orifice. As water enters or drains from the sump, hydrostatic head pressure compresses air inside the pressure tube. If the pressure switch port clogs with grease, the internal diaphragm sticks, or the 120 VAC drain pump motor (5304512762 / 154829101, 20–35 Ω) fails to evacuate water, the board flags i20 or i21 and aborts the wash program.

i20 / i21 failure modes: Clogged sump pressure chamber orifice, defective pressure sensor (5304509705), open drain pump motor winding, crushed pressure sensor rubber seal, or damaged 5 VDC logic rail on the main board. Compare with other dishwasher drain and leak safety systems: Bosch dishwasher E15 flood sensor & base pan diagnostics or LG dishwasher AE / E1 leak sensor float switch diagnostics. Service options: Frigidaire dishwasher repair services.

Safety: Turn OFF the dedicated 15A/20A dishwasher circuit breaker and close the under-sink water supply valve before removing lower access panels or sump components. Live 120 VAC line power is present at the drain pump and main control board terminals.

Step-by-step diagnostic hierarchy

1. Verify error code and inspect tub water level — When i20 or i21 appears:

   • Open door and check standing water level in tub.
   • Water above heating element: Physical drain blockage or failed 120 VAC drain pump.
   • Tub completely empty: Clogged pressure sensor air port or failed pressure switch 5304509705.

2. Inspect and clean lower filter assembly — Remove bottom rack, spray arm, and glass trap filter:

   • Wash fine stainless filter mesh under warm water.
   • Inspect the small pressure sensor inlet hole located in the right-rear well of the plastic sump.
   • Gently clear soil or food debris using a soft nylon brush. Never insert metal drill bits or screwdrivers into the pressure orifice.

3. Access pressure switch sensor (Power OFF) — Remove toe-kick panel and lower insulation barrier:

   • Locate pressure sensor 5304509705 mounted to the lower sump body.
   • Unclip the 3-wire connector plug. Inspect harness pins for green corrosion or detergent moisture.

4. Measure pressure switch 5 VDC logic signal (Live Test) — Reconnect sensor plug, re-apply circuit breaker power, and back-probe the 3-wire harness with a multimeter set to 20 VDC:

   • Pin 1 to Pin 3 (VCC to GND): 5.0 VDC (±0.2 VDC) reference supply from main board.
   • Pin 2 to Pin 3 (Signal to GND) with Empty Tub: ~0.4–0.7 VDC.
   • Signal with Full Tub (1.5 Gallons Fill): ~2.5–3.5 VDC.
   • Result: If reference voltage is 5 VDC but signal remains fixed at 0 VDC or 5.0 VDC during fill/drain, replace pressure switch 5304509705.

5. Test 120 VAC drain pump motor winding (Power OFF) — Disconnect 2-wire connector from drain pump 5304512762:

   • Set multimeter to 200 Ω range and measure across motor terminals.
   • Expected resistance: 20–35 Ω (120 VAC synchronous pump motor).
   • ∞ Ω indicates an open motor coil; < 5 Ω indicates a shorted winding. Replace drain pump.

6. Verify 120 VAC drain pump voltage output (Live Cancel/Drain Test) — Back-probe drain pump connector during a Cancel/Drain command:

   • Expected voltage: 108–132 VAC.
   • If 120 VAC is present but pump only hums without spinning, clear glass/seeds jammed in the impeller or replace the pump.

7. Check drain hose and garbage disposal knockout — Verify drain hose high loop reaches at least 32 inches above the cabinet floor. Confirm sink disposal knockout plug was removed during installation.

Multimeter and safety checks

Disconnect electrical power at the circuit breaker before removing harness connectors.

Component / Test	Setup & Meter Range	Expected Normal Value	Fault / Failure Mode
Board Reference Supply	Pressure sensor VCC to GND, 20 VDC	5.0 VDC	0 VDC (Failed 5V rail on main control PCB)
Pressure Signal (Empty)	Sensor Signal to GND, 20 VDC	~0.4–0.7 VDC	Fixed 5.0 VDC (Triggers false i20 empty error)
Pressure Signal (Full)	Sensor Signal to GND, 20 VDC	~2.5–3.5 VDC	Fixed 0.5 VDC (Triggers false i21 overfill)
Drain Pump Winding	Isolated pump terminals, 200 Ω range	20–35 Ω	∞ Ω (Open coil) or < 5 Ω (Shorted motor)
Water Inlet Valve Coil	Isolated valve leads, 2 kΩ range	1.0–1.4 kΩ	∞ Ω (Open valve coil causing fill failure)
Harness Continuity	Sensor plug to main PCB, 200 Ω range	~0.2–0.8 Ω	∞ Ω (Pin wire severed in door flex area)

Root cause vs repair breakdown

Observable Symptom	Root Cause / Faulty Part	Corrective Repair Action
i20 code, empty tub, 5 VDC present at sensor	Clogged sump pressure chamber orifice or failed sensor	Clean sump port; replace pressure switch 5304509705
i20 code, standing water in tub, pump hums	Jammed drain pump impeller or open pump winding	Clear impeller obstruction or replace pump 5304512762
i21 code, tub overfilling with water	Failed pressure sensor signal or stuck water inlet valve	Replace pressure sensor 5304509705 or inlet valve
i20 code, 0 VDC reference voltage at sensor	Damaged 5V power supply on main control board	Replace main electronic control board

FAQ

What do the i20 and i21 error codes mean on a Frigidaire dishwasher?

Error i20 indicates a drain restriction or low water drainage fault detected by the pressure switch. Error i21 indicates a high water level or overfill condition sensed by the same analogue pressure sensor (5304509705). The main control board halts the cycle to prevent tub overflow.

How do I test the Frigidaire dishwasher pressure switch (5304509705)?

Disconnect power and access the pressure switch under the lower sump. The pressure sensor (5304509705) operates on a 5 VDC reference signal from the main control board. Measure DC voltage at the board connector with the tub empty: signal feedback wire to GND should read ~0.5 VDC when empty, rising smoothly to ~2.5–3.5 VDC as water fills the tub.

Can a clogged pressure sensor air chamber cause the i20 error code?

Yes. Food soil, grease, and hard water scale collect inside the small plastic pressure chamber orifice at the bottom of the sump. When soil blocks the pressure port, air pressure cannot reach pressure switch 5304509705, trapping the sensor signal at “full” or “restricted” and triggering i20.

When to schedule professional service

If 5 VDC reference voltage is missing from the main PCB, or if i20/i21 error codes persist after replacing pressure switch 5304509705 and cleaning the sump pressure chamber, professional Frigidaire dishwasher repair is recommended. Schedule a Frigidaire dishwasher diagnostic →