❄️Air Conditioner

E09

York · YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor

York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor E09 Error Fix: Communication Error Between Indoor and Outdoor Units

The control boards in the indoor and outdoor units are not communicating properly, possibly due to wiring damage or control board failure. This disrupts normal operation and causes system shutdown.

High severity2 fixes available✨ Free fix available

Quick Answer

Error E09 on the York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor means: Communication Error Between Indoor and Outdoor Units. The top-ranked community fix is “Replace Faulty Control Board” (hard difficulty, ~90 min, DIY cost: $0). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · air conditioner

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

Root Cause Analysis

Control Board FailurePrimary

Electrical Fault → Wiring Harness Damaged

When to Call a Professional

While many air conditioner repairs can be done safely at home, consider hiring a qualified technician if:

This is a high severity error — continued use may cause damage or a safety hazard
The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $250-$400.

Other York Models with Error E09

DERA-P036N07 HP 16 SEER

heat_pump · 2 fixes

GM9S080B12MP11 80,000 BTU 96% AFUE Single-Stage Upflow Gas Furnace

furnace · 2 fixes

TM8E100C20MP11 100,000 BTU 80% AFUE Single-Stage Upflow Gas Furnace

furnace · 2 fixes

TM9V080B12MP11 80,000 BTU 96% AFUE 2-Stage Variable-Speed Gas Furnace

furnace · 2 fixes

Other York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor Error Codes

E01

Indoor Temperature Sensor Fault

2 fixes

E02

Outdoor Unit Fan Motor Failure

2 fixes

E03

Refrigerant Leak Detected

2 fixes

E04

Compressor Overcurrent Protection Triggered

2 fixes

E05

Indoor Fan Motor Stall Detected

2 fixes

E06

High Pressure Switch Triggered

2 fixes

E07

Low Pressure Switch Triggered

2 fixes

E08

Drain Pump Failure

2 fixes

People Also Ask About York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor Error E09

What does error code E09 mean on a York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor?

Error code E09 on the York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor means: Communication Error Between Indoor and Outdoor Units. The control boards in the indoor and outdoor units are not communicating properly, possibly due to wiring damage or control board failure. This disrupts normal operation and causes system shutdown.

How do I fix error code E09 on my York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor?

The most successful fix is "Replace Faulty Control Board" (hard difficulty, ~90 minutes). This fix costs nothing. HomeMD has 2 community-ranked fixes for this error.

Is error code E09 on a York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor serious?

This error is rated high severity. You should address it promptly — continued use could cause damage or safety concerns.

Can I fix York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor error E09 myself?

Yes — the top-ranked community fix ("Replace Faulty Control Board") is rated hard difficulty and takes about 90 minutes. Tools needed: Phillips screwdriver, Multimeter.

How much does it cost to repair York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor error E09?

DIY cost: $0. Professional repair typically costs $250-$400. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor have?

The York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor has 8 other known error codes, including: E01 (Indoor Temperature Sensor Fault), E02 (Outdoor Unit Fan Motor Failure), E03 (Refrigerant Leak Detected), E04 (Compressor Overcurrent Protection Triggered), E05 (Indoor Fan Motor Stall Detected), and 3 more.

Which other York models have the E09 error?

Error code E09 also appears on 4 other York models: DERA-P036N07 HP 16 SEER, GM9S080B12MP11 80,000 BTU 96% AFUE Single-Stage Upflow Gas Furnace, TM8E100C20MP11 100,000 BTU 80% AFUE Single-Stage Upflow Gas Furnace, TM9V080B12MP11 80,000 BTU 96% AFUE 2-Stage Variable-Speed Gas Furnace. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor have?

The York YCG42B21S 3.5 Ton 14 SEER Affinity Series Air Conditioner with Scroll Compressor has 8 other known error codes:

E01 — Indoor Temperature Sensor Fault (2 fixes)
E02 — Outdoor Unit Fan Motor Failure (2 fixes)
E03 — Refrigerant Leak Detected (2 fixes)
E04 — Compressor Overcurrent Protection Triggered (2 fixes)
E05 — Indoor Fan Motor Stall Detected (2 fixes)
E06 — High Pressure Switch Triggered (2 fixes)
E07 — Low Pressure Switch Triggered (2 fixes)
E08 — Drain Pump Failure (2 fixes)

Which other York models have the E09 error?

Error code E09 also appears on 4 other York models:

DERA-P036N07 HP 16 SEER (heat pump) · 2 fixes
GM9S080B12MP11 80,000 BTU 96% AFUE Single-Stage Upflow Gas Furnace (furnace) · 2 fixes
TM8E100C20MP11 100,000 BTU 80% AFUE Single-Stage Upflow Gas Furnace (furnace) · 2 fixes
TM9V080B12MP11 80,000 BTU 96% AFUE 2-Stage Variable-Speed Gas Furnace (furnace) · 2 fixes

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