Trane · Furnace

E28 Supply air thermistor out of range or not connected

Low severity Trane S8V2

What the control is telling you

The supply air sensor (BAYSENSC360, plugs into E22) is open/shorted or enabled but not installed.

Applies to: Trane S8V2 only

Likely causes

Sensor enabled but not fitted
Sensor unplugged or damaged

Test and repair steps

Confirm whether BAYSENSC360 is installed; it is off by default in the diagnostics app and must be switched on only when fitted.
Check the sensor is plugged into E22 on the IFC and its wire is intact.
Replace the sensor if it reads open or shorted.

Settings for these units

Clearance to combustibles · Trane S8V2

Cabinet width	Vertical sides / top	Horizontal sides / top
14.5 in.	0 / 1 in.	1 / 2 in.
17.5 in.	0 / 1 in.	1 / 2 in.
21.0 in.	0 / 1 in.	1 / 3 in.
24.5 in.	0 / 1 in.	1 / 5 in.

24 in. front service access.

3 in. in front of the combustion air openings.

Return filter size by cabinet width · Trane S8V2

Cabinet width	Filter
14-1/2 in.	1 - 14 x 25 x 1 in.
17-1/2 in.	1 - 16 x 25 x 1 in.
21 in.	1 - 20 x 25 x 1 in.
24-1/2 in.	1 - 24 x 25 x 1 in.

Filters are field supplied and mounted outside the cabinet.

Over 1600 CFM upflow: return on both sides, one side plus bottom, or bottom only.

Models that show this code

12 models in Trane S8V2

S8V2A040M3PCBS8V2A040M3PDS8V2B060M4PCBS8V2B060M4PDS8V2B080M4PCBS8V2B080M4PDS8V2C080M5PCBS8V2C080M5PDS8V2C100M5PCBS8V2C100M5PDS8V2D120M5PCBS8V2D120M5PD

Other codes on the same units

E13 Blower motor size / OEM ID mismatch
E14 Configuration file error
E17 Blower motor communication error
E23 Menu data not received by combustion micro (CCM)
E24 Internal communication error between ACM and CCM
E25 Orientation sensor out of range
E26 Return static pressure sensor out of range or not connected
E27 Return air thermistor out of range or not connected

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

Open the app

Source: Trane FNR-SVX003A-EN (S8V2 installer's guide) - section Integrated Furnace Control Display Codes, Table 37 Error codes. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.