03 on a Viessmann Vitotronic 200: Short circuit/lead break suction gas temperature sensor
Short answer
On a Viessmann heat pump, 03 means: Short circuit/lead break suction gas temperature sensor. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manuals for this range word it in different ways:
- Short circuit/lead break suction gas temperature sensor.
- Short circuit/lead break, suction gas temperature sensor.
- Configuration fault: Limited or no heat pump and/or heating system functionality Reading an additional code The additional 2-digit code contains further information (additional messages). Each digit is a hexadecimal value. ….
Part involved: Short circuit/lead break suction gas temperature sensor; Short circuit/lead break, suction gas temperature sensor; Configuration fault.
When it shows: Type "Fault" (S) - triggers "05 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Compressor OFF Type "Fault" (S) - triggers "05 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Compressor OFF; Energy statement is not; calculated correctly: See chapter "Diagnosis, Energy statement". Limited or no heat pump and/or heating system functionality Reading an additional code The additional 2-digit code contains further information (additional messages). Each digit is a hexadecimal value. The numbers of the additional messages can be read from the hexadecimal ….
Likely causes:
- Short circuit/lead break suction gas temperature sensor.
- Short circuit/lead break, suction gas temperature sensor.
- 1st digit of the additional code 1st digit 1 Incorrect system scheme for central heating via ventilation unit 2 "Min. suction pressure 5086" set higher ….
- Incorrect solar control unit set ("Type solar control unit 7A00").
- AM1 extension not enabled ("External extension 7010").
- Coolant buffer cylinder is enabled at the same time Values from example 2nd digit of the additional code 2nd digit 1 Incorrect system scheme (contains ….
- Room temperature sensor for cooling set from unavailable remote control.
- "Max. flow temperature heating circuit 200E" set lower than "Min. flow temperature cooling 7103".
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated in 6150133.
Manual reset: Refrigerant circuit messages cannot be acknowledged in the message history (6150133 p.155); acknowledge the resulting 05/07/A9 message on the control unit.
What you can check
- This code is only visible to engineers in the service menu (Diagnosis > Refrigerant circuit > Message history); homeowners see message 05, 07 or A9 - note that code and call your contractor.
- Note the 2-character message code and message text shown on the Vitotronic 200 display (press OK for details) and give them to your heating contractor (operating instructions 5817913 p.56).
- You may acknowledge the message once with OK as described in the Vitotronic 200 operating instructions; if it reappears, do not keep acknowledging it - call your contractor.
- Check the heat pump breaker/isolator in the consumer unit is ON (do not repeatedly reset a breaker or RCD that keeps tripping).
- Check the heating system pressure gauge reading and report a low reading to your contractor; make sure the filling loop is closed.
- Check the outdoor unit (air source models) is not blocked by leaves, debris or snow.
What the engineer will check
- Check resistance value (Pt500A) at the sensor connection of the EEV PCB: See "EEV PCB [2] ".
- Check resistance value (NTC 10 k Ω) at connection J13 (T4) of the EEV PCB: See "EEV PCB [4-3] / [4-4] ".
- Check resistance value (NTC 10 k Ω) at connection J13 (T4) of the EEV PCB: See "EEV PCB [4-6] / [4-7] ".
- Check resistance value (NTC 10 k) Ω at connection J21 (T7) on the EEV PCB: See "EEV PCB [4] ".
- Check resistance value (NTC 20 k Ω) at connection T-SENSOR3 on the main PCB: See "Main PCB [7] / [7-1] ".
- Check and adjust relevant parameters. If necessary, restore factory settings (reset) and reconfigure system. Contact a heat pump specialist certified by Viessmann if the cause ….
Who to ask for: Viessmann-trained heat pump engineer with F-gas refrigeration certification; Viessmann-trained heat pump installer/service engineer.
Certification: F-gas certificate (UK F-gas Regulations; Viessmann: refrigerant work by authorised refrigeration engineers only).
What you might notice
Sources
- Service instructions Vitotronic 200 type WO1C heat pump control unit (air/water split & monobloc, brine/water) (6150133, 2023-07) ↗ · 6150133 VSA00004 · pages 156, 166, 173, 161, 183, 84-85 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026