Viessmann Boiler Error Codes: F2, F4, EE and E8

By Ray Bennett · Updated 17 October 2026 · 9 min read · Checked against the sources at the end

Viessmann Boiler Error Codes: F2, F4, EE and E8

Short answer

Match the Vitodens model before reading the code. Viessmann lists F2 as a tripped high limit and F4 as no flame signal on the 100-W B1HA/B1KA. On the 200-W B2HA 45/60, EE means a missing or weak starting flame signal; E8 means ionization current outside its permitted range. CL and 74 need the exact control identified.

Viessmann boiler error codes make more sense once you have the model beside the message. In Viessmann’s US manuals, F4 on a Vitodens 100-W B1HA/B1KA means no flame signal, while the Vitodens 200-W B2HA 45/60 uses EE for a missing or weak flame signal at startup.

You do not need to take the boiler apart to make a useful start. This guide explains those controls, the checks you can make outside the cabinet, and what the heating contractor will investigate.

Before you start

What to carry: a torch, your phone and the boiler’s paperwork. Photograph the whole display and copy the model and serial number from an accessible label or your service record. Leave the cabinet closed.

Gas or electric? These are gas boilers. Viessmann’s B1HA/B1KA and B2HA manuals cover natural gas and propane, not electric boilers or oil burners.

Which Vitodens? Match the letters after the product name: this page covers B1HA/B1KA 26 to 125 and B2HA 45/60 with the Vitotronic 200 HO1B control. A manual for another Vitodens generation is not the reference used here.

Renting? Send the display photo to your landlord or building manager so they can arrange the repair.

Deal with these before any reset. Overheating or gas that will not shut off. Viessmann’s B1HA/B1KA operating manual says to leave the pump’s electrical supply on and shut off the gas at a location outside the boiler instead.

A gas smell. Viessmann says not to light an appliance, touch electrical switches or use a phone in the building. Leave and call the gas supplier from a neighbor’s phone; if you cannot reach them, call the fire department.

A CO alarm. CPSC says to move outside to fresh air immediately, call 911, count everyone to check that nobody is missing, and stay out until emergency responders allow you back.

Flue gas smell. Viessmann’s B1HA/B1KA operating manual says to turn the heating equipment off, open windows and doors, and inform the heating contractor immediately. If you smell gas or hear a CO alarm, leave and follow the emergency steps above.

Water damage. Viessmann says not to use a B1HA/B1KA if any part has been under water. It requires a qualified heating contractor to inspect it and replace affected controls.

Inside the cabinet. Viessmann’s B1HA/B1KA service manual says there are no user serviceable parts in the boiler, burner or control. Gas pressure measurements, electrode work and electrical tests below describe the contractor’s work.

Match the code to the control

Use the model and the whole display together. These are reading examples, not exact control layouts.

These entries come from Viessmann’s B1HA/B1KA service manual, page 62, and B2HA 45/60 service manual, pages 75 and 76.

Your boiler	Code	Viessmann’s meaning
100-W B1HA/B1KA	F2	Fixed high limit tripped
100-W B1HA/B1KA	F4	No flame signal present
200-W B2HA 45/60	F2	Fixed high limit switch open or activated
200-W B2HA 45/60	EE	Flame signal missing or too weak at burner start
200-W B2HA 45/60	E8	Ionization current outside the permissible range

On the B2HA’s HO1B control, Viessmann says pressing OK brings up the fault and the question mark button brings up further information. Include the description as well as the code when arranging service. Its manual gives “Outside temp sensor 18” as an example of the information the contractor needs.

F2 and F4 on the Vitodens 100-W

Check 1A service visit; the repair depends on the checks

F2: the high limit has tripped

For the B1HA/B1KA, Viessmann’s F2 checks are the water level, circulation pump, air in the system, fixed high limit and its wiring. For the B2HA 45/60, its F2 row gives the same areas to investigate.

The useful thing you can pass on is the pressure gauge reading, together with whether the boiler was hot when it stopped. Leave refilling, bleeding at the boiler and testing the limit to the contractor in this fault situation.

Viessmann’s list includes the pump and water circulation as well as the limit itself. Ask which check failed before agreeing to a replacement limit. A separate guide explains a boiler circulator pump that is not working.

Check 2External observations first; a service visit for testing

F4: the control is not receiving a flame signal

On the B1HA/B1KA, Viessmann tells the contractor to check ignition electrodes and wires, ionization current, gas pressure, the gas valve, ignition components and the condensate drain. F4 alone does not select one replacement part from that list.

Check the fuel supply without opening the boiler. For a B1HA/B1KA with no fuel, Viessmann’s operating manual tells propane owners to check their reserves and reorder if needed. For natural gas, it directs owners to the shutoff valve and, if necessary, their gas utility. A valve closed for a known safety fault stays closed until that fault is resolved.

Mention a drain problem. Viessmann specifically warns that a blocked condensate drain can cause F4 on the B1HA/B1KA. Its service manual says not to restart immediately if the combustion chamber lining has become wet, because that will damage it. Let the contractor inspect the trap and chamber.

Viessmann's B1HA/B1KA checks follow two different paths: water circulation for F2, and ignition, flame sensing, gas and drainage for F4. Internal checks belong to the contractor.

EE and E8 on the Vitodens 200-W

Check 3A contractor's diagnosis before choosing parts

EE: the starting flame signal is missing or weak

For the B2HA 45/60, Viessmann’s EE row calls for checking the gas supply and regulator, gas train, ionization electrode and its cable, ignition components and condensate drain. The manual lists detailed fault 132 beside EE.

Tell the contractor what happened at the start: did you hear ignition, did the burner run briefly, or did the message appear without an obvious attempt? Describe what you noticed without removing a panel to watch the flame.

Viessmann distinguishes EE from EF on these models. EF means the flame was lost immediately after it formed, during the safety time. EE and EF have different meanings, so report the letters exactly as displayed.

Check 4Gas and electrode tests by a heating contractor

E8: the flame sensing current is out of range

Viessmann’s B2HA 45/60 manual defines E8 as ionization current outside the permissible range and lists detailed fault 189 beside it. Viessmann describes the ionization signal as an input to its combustion control.

Its E8 checks include gas pressure, the gas flow limiter, gas valve and cable, the selected gas type, and the ionization electrode’s gap and contamination. Those are measurements and inspections for the contractor, not a reason to adjust the gas valve yourself.

There is another E8 in this manual: E8:1 in the Coding 2 settings table, marked “NOT USED” for these models. That settings entry is separate from the E8 fault row. Do not enter the coding menu or change a setting to try to clear a fault.

Can you reset it?

Check 5No part needed for the reset; a recurring fault needs service

Use the reset instruction for your display

First deal with the safety conditions above. For F2 or suspected condensate flooding, let the contractor resolve the cause before using the reset steps. Before resetting a B1HA/B1KA, Viessmann tells owners to inspect the outside vent termination and remove any blockage if possible. Report anything you cannot safely reach from the ground; its manual directs an owner to a heating contractor if a blockage is not obvious or cannot be removed.

B1HA/B1KA with R displayed. In its operating instructions, page 17, Viessmann says a flashing fault symbol with R means the burner is locked out. Hold R for about two seconds. If the fault no longer exists, the normal display returns.

Viessmann warns against several resets in quick succession and says to notify the heating contractor if the fault returns. That is the stopping point, not a prompt to keep trying.

B2HA with “Combustion controller” displayed. Viessmann’s HO1B operating manual says to press R, acknowledge the fault and notify the contractor if it recurs. It does not give the B1HA’s two second hold for this control.

Acknowledging is separate. On the HO1B, Viessmann says acknowledging a fault moves its message to the menu. An unresolved fault reappears the following day. The message can disappear from the main screen even though the fault is still there.

CL, 74 or a code that is not in this list

I could not verify a fault definition for CL or 74 in these two US service manuals. Their fault tables are on B1HA/B1KA pages 61 and 62 and B2HA 45/60 pages 71 through 77. This page does not assign either code a guessed meaning.

Include any prefix, decimal point and accompanying words. For another control, the next step is its matching Viessmann manual, not a reset sequence borrowed from the B1HA or B2HA.

If there is no fault message and the problem is repeated starts and stops, use a boiler that keeps turning off. That guide also covers stops that are part of normal heating operation.

What each one takes

What you have found	What it takes
Wrong manual or incomplete message	The full display and matching model details before diagnosis
B1HA/B1KA propane supply empty	A fuel delivery, as Viessmann’s operating manual directs
F2 on the models above	Viessmann’s water, pump and high limit checks by the contractor
B1HA/B1KA F4 or B2HA 45/60 EE	Viessmann’s ignition, gas, flame signal and drain checks; parts only as needed
B2HA 45/60 E8	Viessmann’s gas and ionization electrode checks
A fault returning after reset	A service visit to find and correct the cause

Questions people ask

Does F2 mean the temperature limiter needs replacing?

Not from that code alone. Viessmann’s B1HA/B1KA and B2HA 45/60 F2 rows include the water level, circulation pump and air in the system before checking the high limit and its wiring.

Does F4 mean the gas valve has failed?

Viessmann’s B1HA/B1KA manual defines F4 by the missing flame signal. The gas valve is one item on its test list, alongside ignition, flame sensing and condensate drainage.

Are EE and E8 the same error?

No. On Viessmann’s B2HA 45/60, EE concerns a missing or weak signal at burner start. E8 concerns ionization current outside its permitted range. The checks overlap, but the manual gives separate fault entries.

Why is the fault back after I acknowledged it?

Viessmann’s HO1B manual says an unresolved fault is displayed again the following day. Acknowledging the message only moves it to the menu.

Why does the boiler make hot water but leave the rooms cold?

Viessmann’s B1HA/B1KA operating manual lists domestic hot water priority as one explanation: wait for the tank to heat, or on the B1KA stop drawing hot water. If heating still fails, start with the boiler not working checks.

The other boiler guides: boiler pressure, a boiler making noise and a boiler that smells.

Sources: Viessmann Vitodens 100-W B1HA/B1KA 26 to 125 Installation and Service Instructions 5784 568-22 (08/2025), Operating Instructions 5784 570-07; Vitodens 200-W B2HA 45/60 Service Instructions 5683 704-22, Vitodens 200 Series with Vitotronic 200 HO1B Operating Instructions 5683 712-01 (03/2014); CPSC Carbon Monoxide Questions and Answers