York furnace 6 red flashes: pressure switch lockout or gas valve error

Short answer 6 red flashes on York, Coleman and Luxaire furnaces mean the pressure switch opened repeatedly in one call for heat, giving a 1-hour lockout; on the modulating YP9C, CP9C, LP9C, TP9C, TM9M and TPLC family it is a gas valve error. Both are technician work. See what to check

Furnace control LED

6 red flashes

“Repeated 3 Red”

Technician

Printed on 20 model series · 13 documents

TM8X, TMLX, TM9E, TM9T, TG9S, GG9S, TM9X, TM9V, DGAX, RGF19*E, TM9Y, TM9V*C, TM8V*C, TMLV*C, TM8T*MP, TMLT*MP, TG8S*MP, TGLS*MP, GG8S*MP, GGLS*MP · 998492-UIM-C-1013 p. 26; 6019630-UIM-F-0423 p. 36; 1083286-UIM-A-0114 p. 39; 1083287-UIM-A-0114 p. 40; 1083288-UIM-A-0114 p. 38; 1083294-UIM-A-0114 p. 44; 5483101-UIM-A-1118 p. 29; 6019627-UIM-F-0423 p. 36; 5750144-UIM-H-0423 p. 37; 5750149-UIM-I-0423 p. 40; 5750148-UIM-D-0423 p. 30; 995472-UIM-B-0713 p. 28; 998491-UIM-B-1013 p. 29

The lamp blinks 6 times, then pauses. It shows the count only; the timing on your board may differ.

What it means

6 red flashes have two different meanings, depending on the series.

On most York, Coleman and Luxaire furnaces, the pressure switch opened four times during the call for heat while the unit was operating. The furnace locks out for 1 hour and then restarts. The installation manuals point to a faulty inducer, a blocked vent pipe or a faulty pressure switch (5750149-UIM-I-0423, p. 38; 6100757-UIM-C-1124, p. 58). The Y91E, RG19 and Y92E manuals count five openings instead of four (6125049-UIM-C-0624, p. 49; 6154201-UIM-B-1224, p. 78). The label printed with the wiring diagram calls it “Repeated 3 Red” on older and 2023 manuals and “PS CYCLE LOCKOUT” on the Y81E, RL18, Y82E, Y91E, RG19, Y92E and Y92V (5750149-UIM-I-0423, p. 40; 6125049-UIM-C-0624, p. 52; 6553957-UIM-A-0626, p. 96). For comparison, 3 red flashes mean the pressure switch contacts are open when they should be closed (5750149-UIM-I-0423, p. 37).

On the modulating furnaces it is a gas valve fault. The YP9C, CP9C, LP9C and TP9C manuals say “Gas valve communication error.” (5750151-UIM-G-0423, p. 37; 1083292-UIM-A-0114, p. 41). The TM9M manual says the same and adds checks of the wiring from the board to the gas valve, the air pressure sensor connections, and the pressure switch hoses and connections (1083293-UIM-A-0114, p. 39). The TPLC, YPLC, CPLC and LPLC manual says “Current failure on modulating gas valve.” (987158-UIM-B-1013, p. 30). On all of these the label reads “Check gas valve wiring” (5750151-UIM-G-0423, p. 39; 987158-UIM-B-1013, p. 32).

The modulating manuals do not describe a lockout for this code.

Check these first

The owner’s manuals 1010352-UUM-O-0423 and 6100761-UUM-C-1124 have no entry for 6 red flashes. The only red pattern they list is “Rapid red flashes”, with the instruction to contact your local dealer, contractor, or service provider (1010352-UUM-O-0423, p. 5). The LED is behind a clear view port in the blower compartment door (1010352-UUM-O-0423, p. 5).

For a furnace that is not operating correctly, the manual lists visual checks to make before that call. They are the same for every code. In the manual’s order:

1. Check that electrical power to the furnace is turned on (1010352-UUM-O-0423, p. 5).
2. Check that the manual gas shut-off valve in the gas piping supply is in the on position (1010352-UUM-O-0423, p. 5).
3. Check that the on/off switch on the gas valve is in the on position (1010352-UUM-O-0423, p. 5). The manual reaches this switch by setting the thermostat to its lowest setting, turning off all electric power to the appliance and removing the furnace burner access panel or door (1010352-UUM-O-0423, p. 4). Use only your hand on the switch, never tools; if it does not move by hand, do not try to repair it, and call a qualified service technician (1010352-UUM-O-0423, p. 3). Turning it back on follows the full operating instructions: turning the furnace off and on.
4. Check that the furnace blower access panel or door is correctly positioned. The electrical power supply is cut off if this door is removed (1010352-UUM-O-0423, p. 5).

6100761-UUM-C-1124 lists the same checks (pp. 10–11).

On most series a blocked vent pipe is among the causes. The owner’s manual has one owner check that touches the vent, and it belongs to its carbon monoxide warning, not to this code: check that the furnace vent and air intake terminals are not obstructed in any way during all seasons (1010352-UUM-O-0423, p. 1).

When to call a licensed technician

• The inducer, the vent pipe and the pressure switch (5750149-UIM-I-0423, p. 38).
• On the modulating furnaces, the gas valve and its wiring; on the TM9M also the air pressure sensor connections and the pressure switch hoses (1083293-UIM-A-0114, p. 39; 5750151-UIM-G-0423, p. 39).

The 2014 manual for the TP9C, YP9C, CP9C and LP9C warns never to bypass any safety control to allow furnace operation and never to adjust the pressure switch to allow furnace operation (1083292-UIM-A-0114, p. 41). Call as well if 6 red flashes come back after the 1-hour lockout.

Notes for different models

Series	Label on the wiring diagram	Installation manual text	Source
TM9V*C; TM8V*C, TMLV*C (2013 and 2023); TM9V (2014); TM9Y; TM9T; TG9S, GG9S; TM9X; TM9E (2014 and 2023); RGF19*E; TM8T*MP, TMLT*MP; TG8S*MP, TGLS*MP, GG8S*MP, GGLS*MP; TM8X, TMLX	“Repeated 3 Red”	Pressure switch opened four times during the call for heat; 1-hour lockout, then restart	5750149-UIM-I-0423, pp. 38, 40; 5750148-UIM-D-0423, pp. 27, 30; 1034867-UIM-B-0913, pp. 28, 31; 1083294-UIM-A-0114, pp. 42, 44; 5750144-UIM-H-0423, pp. 35, 37; 1083286-UIM-A-0114, pp. 37, 39; 1083287-UIM-A-0114, pp. 38, 40; 1083288-UIM-A-0114, pp. 36, 38; 1083163-UIM-A-0214, pp. 36, 38; 6019630-UIM-F-0423, pp. 34, 36; 6019627-UIM-F-0423, pp. 34, 36; 995472-UIM-B-0713, pp. 26, 28; 998491-UIM-B-1013, pp. 27, 29; 998492-UIM-C-1013, pp. 24, 26
Y81E, RL18, Y82E	“PS CYCLE LOCKOUT”	Four times; 1-hour lockout, then restart	6100757-UIM-C-1124, pp. 58, 62; 6100760-UIM-C-1124, pp. 58, 62; 6142403-UIM-C-1124, pp. 59, 63
Y91E, RG19, Y92E	“PS CYCLE LOCKOUT”	Five times; 1-hour lockout, then restart	6125049-UIM-C-0624, pp. 49, 52; 6125051-UIM-C-0624, pp. 49, 52; 6154201-UIM-B-1224, pp. 78, 82
Y92V	“PS CYCLE LOCKOUT”, display 06	Four times; 1-hour lockout, then restart	6553957-UIM-A-0626, pp. 89, 96
YP9C, CP9C, LP9C, TP9C	“Check gas valve wiring”	“Gas valve communication error.”	5750151-UIM-G-0423, pp. 37, 39; 1083292-UIM-A-0114, pp. 41, 43
TM9M	“Check gas valve wiring”	Gas valve communication error; check the wiring from the board to the gas valve, the air pressure sensor connections, the pressure switch hoses and connections	1083293-UIM-A-0114, pp. 39, 41
TPLC*C, YPLC*C, CPLC*C, LPLC*C	“Check gas valve wiring”	“Current failure on modulating gas valve.”	987158-UIM-B-1013, pp. 30, 32
DGAX	“Repeated 3 Red”	No text; label only	5483101-UIM-A-1118, p. 29

The TM9V*C manual is an example of label and text worded differently: the label says “Repeated 3 Red”, the text describes four openings of the pressure switch (5750149-UIM-I-0423, pp. 38, 40). The DGAA and DGAH owner’s manual for manufactured-home furnaces has no 6 FLASH entry in its list (5165697-BUM-C-0818, p. 8).

Related York, Coleman and Luxaire codes

• 3 red flashes “Vent OR termination problem”
• 2 red flashes “Check pressure switch wiring”

See also

• Heat pump vs gas calculator
• Furnace and HVAC tax credits for 2025 and 2026: 25C ended after 2025
• Form 5695 for 2025 and 2026: QMID, lines, carryforward
• How a gas furnace lights, and how the control board blinks a failure code
• Home maintenance schedule from the manuals: monthly to yearly
• Winter home maintenance checklist: furnace, boiler, water heater
• Water heater or furnace closet: clearance and air requirements

Other gas furnaces: Carrier, Goodman, Lennox, Rheem furnaces, Trane and American Standard

All York, Coleman and Luxaire codes

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