This is a reference guide, not a repair manual. York, Coleman, and Luxaire share Johnson Controls control boards, so the codes below read the same across all three brands. One rule before you start: the legend printed on your furnace’s blower-door label is the authoritative key for the exact board installed in your unit. Board generations vary, and the colors and counts can shift slightly between revisions, so we always read against that label rather than a generic chart. Gas-furnace codes touch combustion and safety circuits — use this to understand what your furnace is telling you, then call a licensed technician for anything past a filter change or a single reset.
Two ways a York reports faults
Which method your system uses depends on the thermostat and equipment generation:
- Conventional control board (most TM9V, TM8V, and earlier furnaces) — a single status LED flashes green, amber, or red through the access-panel sight glass. You count the flashes within each color.
- Communicating Affinity (YHCT / Hx / Hx3 touchscreen) — the thermostat and equipment talk over a serial bus, and faults appear as descriptive on-screen messages, not flash counts.
Context 1 — conventional board LED flash codes
On a conventional York board you read color first, then count. Confidence notes reflect how consistently each code is documented across York/Coleman/Luxaire references; confirm against your blower-door legend.
Green — status
| Code | Meaning |
|---|---|
| 1 green (or steady) | Normal status, no active call for heat or cool — the board is healthy. |
Amber — normal calls and soft warnings
| Code | Meaning |
|---|---|
| 1 amber | Normal cooling call. |
| 2 amber | Normal heating call. |
| 3 amber | Cycle ending / reaching setpoint. |
| 4 amber | Restricted circulating air — check filter and registers. |
| 5 amber | Restricted vent or combustion air. |
| Rapid amber | Low flame sense — clean or replace the flame sensor before it locks out. |
Red — hard faults
| Code | Meaning |
|---|---|
| 2 red | Pressure switch stuck closed. |
| 3 red | Pressure switch stuck open — often a clogged condensate trap or weak inducer. |
| 4 red | Open high-limit or blown 24V fuse — usually restricted airflow. |
| 5 red | Rollout or auxiliary limit open — stop and call; possible combustion issue. |
| 6 red | Modulating gas-valve current fault (varies by board generation). |
| 7 red | Ignition lockout — no flame proven after three trials. |
Flame-sense current is the number behind the rapid-amber and seven-red codes: a healthy York reads about 3.7 microamps at the flame sensor, the low-signal warning starts near 1.5 microamps, and the board drops to lockout around 0.1 microamps. We measure it at the test pad rather than guessing.
Context 2 — communicating Affinity faults
The communicating Affinity line is different: there is no flash count to read. The YHCT, Hx, or Hx3 touchscreen thermostat displays a descriptive fault, and the codes are categories rather than alphanumeric strings. Common categories include:
- Out-of-range or failed sensor — a temperature or pressure sensor reading outside its valid window.
- High-limit / 24V fuse open — the communicating equivalent of the four-red flash.
- Rollout / auxiliary limit open — a safety trip on the combustion path.
- Gas-valve circuit fault — a shorted or open gas-valve control circuit.
- No-ignition lockout — flame not proven, same root causes as a seven-red lockout.
- Loss of communication — the thermostat and equipment are not talking; a wiring or board fault, not a mechanical one.
We describe the categories here rather than invent alphanumeric codes, because the on-screen wording varies by firmware. The diagnosis is the same regardless: read the on-screen fault, then confirm the underlying cause on the meter.
What a code does — and does not — tell you
A flashed code or on-screen fault names the subsystem, not the failed part. A seven-red lockout could be a worn ignitor, a dirty flame sensor, a closed gas valve, or a venting fault — four different repairs at four different prices. A four-red high-limit is usually just a clogged filter, but it can also be a failing blower. That is why we read the code as a starting point and then confirm with meter readings before quoting a part. On a 2012–2016 TM9V with intermittent ignition that clears before we arrive, we also test for the known control-board cohort failure regardless of what the LED last showed — details on our York furnace not heating page.
From code to repair
Once the code points at a subsystem, these are the York repairs it usually leads to, flat-rate from our SoCal tickets:
| Code points to | Typical repair |
|---|---|
| 7 red / no-ignition (ignitor) | Hot-surface ignitor $245–$485 |
| Rapid amber (flame sense) | Flame sensor clean or replace $185–$295 |
| 2/3 red (pressure switch) | Pressure switch / inducer $185–$1,100 |
| Gas-valve fault | Gas valve $385–$685 |
| Intermittent ignition (TM9V cohort) | Ignition control board $385–$685 |
Diagnostic is $89 ($149 after-hours), credited to the repair. Full no-heat detail is on our York furnace not heating and York furnace repair pages.
Do not keep resetting a locked-out furnace
The most common mistake we see is repeatedly cycling power to clear a red-flash lockout. You can clear a one-time lockout with a single power cycle, but if it returns, stop — repeated retries can mask a venting, gas-supply, or limit problem and stress the board. Note the flash count or on-screen message and call. For the broader troubleshooting chain, see our furnace ignitor failure and furnace blowing cold air guides.
Coleman, Luxaire, and the rest of the lineup
Because Coleman and Luxaire run the same Johnson Controls boards, every code above applies to them too — same colors, same counts, same communicating categories. For repair detail, see York furnace repair, York AC repair, and York heat pump repair, or the full lineup on our York brand page.