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Carrier 59TP6C two-stage condensing with InteliSense Furnace Codes
Older 59TP6A and 59TP6B boards show two-digit flash codes only; use their own service labels.
| Code | Meaning | What to check |
|---|---|---|
| 10.1 | L1 polarity fault (LED flashes rapidly). | Swap hot and neutral at the furnace; verify ground. |
| 12.1 | W (heat call) on at power-up. | Thermostat and W wiring. |
| 13.1 | Limit lockout: a switch in the main limit circuit open longer than 3 minutes. | Filter, ductwork, blower speed and motor, limit wiring. How to fix → |
| 14.1 | Ignition lockout after 4 consecutive ignition tries. | Gas supply, igniter, flame sensor, ground. How to fix → |
| 14.2 | Flame lost 3 times after 70 seconds of heating. | How to fix → |
| 14.3 | Lockout: 7 loss-of-flame events during one heat request. | How to fix → |
| 14.4 | Lockout: 7 low pressure switch (LPS) open events during one heat request. | How to fix → |
| 15.1 | Lockout: no blower RPM detected. | Blower motor, its power and harness. |
| 19.1 | InteliSense communications loss. | |
| 21.1 | 24 V AC sensed on the gas valve when it shouldn't be. | Control board; shut the gas off if the valve stays open. |
| 22.1 | False flame (flame sensed when it shouldn't be). | Flame sense circuit shorts; slow-closing gas valve. |
| 23.4 | Low pressure switch (LPS) stuck closed. | How to fix → |
| 23.5 | High pressure switch (HPS) stuck closed. | How to fix → |
| 24.1 | Fuse fault. | Find the short in the 24 V wiring before replacing the 3 A fuse. How to fix → |
| 25.1 | No program in the control. No heating operation. | Reprogram with the program number on the rating plate; replace the control if it persists. |
| 25.2 | Corrupted program file. No heating operation. | Reprogram with the service app or a super plug. |
| 25.3 | Twinned units not identical (program numbers don't match). Main unit will not heat. | Twinned furnaces must be the same model and program. |
| 25.4 | Main program invalid; running on the backup program. Still operates normally. | Reprogram the control. |
| 25.5 | Installer settings corrupted; running on default settings. | Re-enter installer settings or reprogram. |
| 25.6 | Wrong program for this control. No heating operation. | Reprogram so the program matches the control. |
| 27.1–27.3 | Program in the super plug missing, not recognized or corrupted. | Remove the super plug and retry, then try another super plug; replace the control if it still fails. |
| 31.6 | Open secondary (high) pressure switch (HPS). | How to fix → |
| 31.7 | HPS failed to close within 75 seconds going from low to high heat. High heat locked out for the next cycle. | How to fix → |
| 32.2 | Open main (low) pressure switch (LPS). | How to fix → |
| 33.1 | A switch opened in the main limit circuit. | How to fix → |
| 33.2 | Lockout of high heat for the current cycle. | How to fix → |
| 34.1 | Ignition fault during four consecutive ignition trials. | How to fix → |
| 34.5 | Low heat flame lost before the blower on-delay. | How to fix → |
| 34.6 | Low heat flame lost after the blower on-delay. | How to fix → |
| 34.7 | High heat flame lost before the blower on-delay. | How to fix → |
| 34.8 | High heat flame lost after the blower on-delay. | How to fix → |
| 41.1 | No blower RPM at start-up. | Blower motor, its power and harness. |
| 41.2 | No RPM while the blower motor should be running. | Blower motor, its power and harness. |
| 43.1 | High pressure switch closed before the low pressure switch. | How to fix → |
| 45.1 | Internal control error. | Cycle power; if 45 repeats, replace the control. |
| 45.2 | Gas valve relay (GVR) not closing. | Cycle power; if 45 repeats, replace the control. |
| 45.3 | Micro EEPROM error. | Cycle power; if 45 repeats, replace the control. |
| 45.4 | Micro loss of communication. | Cycle power; if 45 repeats, replace the control. |
| 46.1 | Momentary loss of power. | |
| 52.1 | Supply air temperature sensor (SAT) open. | |
| 52.2 | Supply air temperature sensor (SAT) shorted. | |
| 53.1 | Return air temperature sensor (RAT) open. | |
| 53.2 | Return air temperature sensor (RAT) shorted. |
How to read the codes
- The display shows major.minor: the first two digits are the major code, the third is the minor code. The door LED flashes only the major code: short flashes for the first digit, long flashes for the second (13 = 1 short, 3 long).
- Normal displays: iDL idle, Ht1/Ht2 low/high heat, CL1/CL2 low/high cool, Hpd heat pump defrost, CFn/CF2/CF3 continuous fan, bLr secondary twinned furnace blower.
- Stored faults: with 115 V on, door switch held in and no thermostat call, press MENU/SELECT until FLt shows, then NEXT/OPTION to step through the last 7. Clear with CLr.
Codes point to a circuit, not a part. Test before replacing anything, and never jumper a limit, rollout or pressure switch to keep a furnace running. Gas and line-voltage work is for trained technicians.
Source: Carrier 59TP6C Installation, Start-up, Operating and Service Instructions (59TP6C-03SI), Fig. 60 Service Label status code table and Table 21. The "meaning" column follows the manufacturer's wording; "what to check" is our field summary. Always go by the label on the furnace you're working on.
Related
- How to read furnace LED flash codes
- Furnace pressure switch troubleshooting
- Flame sensor microamps and cleaning
Other brands
- Lennox Merit ML180UH (80% single-stage)
- Carrier 58CVA / 58CVX (80% variable-speed two-stage)
- Rheem / Ruud R96V / 96MDV (96% two-stage communicating)
- Goodman / Amana GR9S80 / GD9S80 (80% single-stage)
- Trane / American Standard S9X1 / S9X2 / S9B1 (96% condensing)
- Lennox SL280UHV (80% two-stage variable speed)
- Goodman / Amana / Daikin GM9S96 / GC9S96 / GM9S92 (96% and 92% condensing, single-stage)
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