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York Furnace Error Codes

Updated · by Aurora Star Tech Inc.

20 York Furnace error codes and diagnostic codes, with causes and troubleshooting steps for each. Select a code, or find your model below.

Homeowner with a furnace problem? Call (647) 657-2977 or book a service call — licensed technicians across Vaughan and the GTA.

York Furnace error codes list

CodeMeaningSeverity
1 red flashFlame detected with gas valve offCritical
2 red flashesPressure switch closed when it should be openMedium
3 amber flashesW2 call without W1Low
3 double red flashesSecond-stage pressure switch not closingMedium
3 red flashesPressure switch open when it should be closedHigh
4 amber flashesCooling call (Y) without fan call (G)Low
4 red flashesMain limit switch openHigh
5 red flashesRollout switch open / limit circuit open over 15 minCritical
6 red flashesPressure switch cycling lockoutMedium
7 red flashesIgnition failure lockout (retries)High
8 red flashesFlame lost repeatedly (recycles)High
9 red flashesPolarity reversed or bad groundMedium
10 red flashesGas valve powered with no heat callCritical
11 red flashesLimit open 5-15 minutes - blower failureHigh
12 red flashesHot surface igniter open / igniter failureHigh
13 red flashesHigh-fire pressure switch openMedium
LED steady offBoard LED dark - no power to controlHigh
Rapid amber flashWeak flame signalMedium
Rapid red flashTwinning error or wrong 24 V phasingMedium
Steady on (any color)LED lit solid - internal control faultHigh

Find codes by York model

TM9V040A10TM9V060B12TM9V080B12TM9V080C16TM9V100C16TM9V100C20TM9V120D20

Furnace troubleshooting guides

York Furnace specs and setup data

Homeowner help: Furnace Not Turning On: What to Check · Furnace Blinking Light: What the Flash Codes Mean

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.

© 2026 Aurora Star Tech Inc. All rights reserved. This page may not be copied, republished or used to train other systems without written permission.

Emergency Furnace Repair

647-657-2977