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Bosch · Heat pump

E45 Th temperature sensor fault

Medium severity Bosch IDS Premium Connected

What the control is telling you

The Th sensor on the outdoor unit reads open or shorted.

Applies to: Bosch IDS Premium Connected BOVA36-20 and BOVA60-20 R-454B heat pump outdoor units

Likely causes

  • Open or shorted sensor
  • Loose connection at the Th sensor port

Test and repair steps

  1. Warning: Switch off power and wait 3 minutes before measuring resistance or touching boards.
  2. Check the Th connection.
  3. Test Th for open or short and replace it if failed.
  4. Replace the control board if the sensor is good.

Models that show this code

2 models in Bosch IDS Premium Connected

BOVA36-20BOVA60-20

Other codes on the same units

  • E41 T3 temperature sensor fault
  • E42 T3L temperature sensor fault
  • E43 T4 temperature sensor fault
  • E44 T5 temperature sensor fault
  • E51 Input voltage out of range
  • E52 DC bus voltage out of range
  • E81 EEV coil fault
  • F1 High pressure switch protection

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Source: Bosch IDS Premium Connected installation BTC 762003301 D (02.2025), Fault Code Table 22 and 18.12 Error Code Troubleshooting. 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.