Trane furnace Which Trane code system you have: Trane furnaces use either flash codes or a seven-segment display, and they share no numbering

Older and single-stage Trane furnaces count LED flashes, 2 through 9. Two-stage variable speed furnaces such as the S9V2 use a seven-segment display showing codes like E2.1 and E3.2, plus a menu holding the last six faults. Neither system's numbering means anything on the other.

Applies to: Trane and American Standard gas furnaces. Read this first if you are looking up a Trane code, because two entirely different diagnostic systems are in use.

What it means

This is a cleaner split than the ones on Lennox or Rheem, because the two Trane systems do not share a numbering scheme at all — there is no number that means one thing on one and something else on the other. What they share is the brand, which is enough to send someone to the wrong table. A Trane flash code is a count of blinks on a single LED: two flashes is a system lockout, four is an open high limit, five is flame sensed when none should be present. A Trane seven-segment code is alphanumeric and appears on a small display on the integrated furnace control, with a menu system operated by Menu and Option buttons. If you are counting anything, you are on the flash code system. If you are reading characters, you are on the seven-segment system.

Most common causes

Trane sells both control platforms concurrently, in different product lines.
Single-stage furnaces generally use the flash code integrated furnace control.
Two-stage variable speed furnaces such as the S9V2 use the seven-segment control.
The two documents are separate installer's guides with no cross-reference between them.

How to diagnose it

Look at what the furnace is showing. A single light blinking a count is the flash code system; characters on a small display are the seven-segment system.
The seven-segment control has Menu and Option buttons next to the display. The flash code control does not.
On the seven-segment control the display shows something at all times, including IdL for idle and Xt1 for first stage heating — it is not only used for faults.
If the code was reported second-hand as a number with no context, establish which it was before acting.

How to fix it

Nothing to fix. This page exists so a code is read against the right table.
Once identified, follow the matching pages on this site.

Notes

The seven-segment control stores the last six faults in a menu, which is genuinely useful — a fault that has cleared itself is still recorded. Hold the Option button for five seconds on that menu to clear the list.

All codes for this manufacturer

Trane and American Standard furnace flash codes — every code, with what differs between models.

This code is not a homeowner repair. Faults in this group involve the gas valve, the burner compartment, or the heat exchanger — the parts whose failure can put combustion products, including carbon monoxide, into the air the house breathes. Do not reset it repeatedly to keep the heat on. Have it looked at by a licensed technician, and make sure there is a working carbon monoxide alarm on every level of the home, including the level the furnace is on.

Sources

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.