Bosch Mini Split Error Codes: EL, EH, EC, P6 and What They Mean

Bosch mini split error codes are short display messages — or, on units without a display, counted blinks of the indoor lamps — that tell you which internal self-check failed. The awkward part with Bosch specifically is that there is no single list. Three different code sets are in service in North American homes right now, and the same characters can mean different things in each one.

This page carries all three, taken from the Bosch Home Comfort service and installation manuals for the Climate 5000 range, plus the part almost nobody explains: on a multi-zone system, the outdoor board and the indoor display show different codes for the same fault.

Which Bosch system do you have?

Before reading any table, work out which of the three code sets applies. Getting this wrong is the most common reason a Bosch mini-split error code looks like it means something alarming when it does not.

Gen 2 and legacy single-zone

One indoor head paired with one outdoor unit, installed roughly between 2019 and 2021, showing short codes such as E1, E5 or P3. The lamp patterns for this generation put outdoor faults on a lit TIMER lamp, which no other Bosch generation does.

Gen 3 single-zone

Wall-mounted, four-way cassette and ducted Climate 5000 systems from 2022 onwards. The giveaway is the shape of the code itself: two parts with a space, such as EL 01 or PC 02. This is the set Bosch still publishes service manuals for, most recently in 2025.

Multi-zone

Two or more indoor heads on a single outdoor unit. This is the awkward one, because the outdoor board and the indoor head do not agree on what to call a fault. Everything on this page about P6 and P0 applies to multi-zone systems only.

Three quick ways to tell them apart:

• A code with a space in it — EL 01, EH 60, PC 02 — is a Gen 3 single-zone code.
• One indoor head, one outdoor unit, and a short code like E1 or P3 is Gen 2 or legacy.
• More than one indoor head on a single outdoor unit is multi-zone, and the code you are looking at depends on where you read it.

If you are not sure, the model number on the outdoor unit’s data plate settles it. Bosch publishes the manual for every ductless model, and the error-code table is always in the back of the installation or service manual.

Where the code appears on a Bosch mini-split

Bosch shows fault information in up to four places, and they do not all carry the same amount of detail:

• The indoor unit’s LED display
• The RUN and TIMER indicator lamps
• The wired wall thermostat, where one is fitted
• The outdoor unit’s own control board

The indoor LED display

A small display behind or beside the louvre on wall-mounted heads. This is where a homeowner will normally see the code, and it is the display the FAQ answers on this page assume unless it says otherwise.

The RUN and TIMER lamps

Units without a numeric display still report the code, by flashing it. This is covered in the next section.

The wired wall thermostat

Gen 3 systems fitted with the optional wired wall thermostat mirror the code there, which is often easier to read than squinting at the head.

The outdoor control board

Multi-zone outdoor units carry their own display with their own code set. This is the one a technician reads, and it is the reason the two numbers you are given may not match.

A code seen on the outdoor board and a code seen on the indoor display are not interchangeable. Note down which one you read.

How to read the RUN and TIMER blink patterns

If your Bosch head has no numeric display, the code is still there. It is counted out on the lamps: a number of RUN flashes, combined with what the TIMER lamp is doing.

Count the RUN flashes twice before you act. The gap between repeats is longer than the gap between flashes, which is how you find the start of the pattern.

Codes that are not faults at all

This is the fastest win on the page. Several Bosch displays look like error codes and are not. Bosch’s own service manual lists them under the heading “Normal Display, not error code”.

The two that generate the most unnecessary calls

• dF in winter, mistaken for a breakdown because the unit stops heating and steams
• CL at power-on, mistaken for a fault code because it appears in the same place a real code would

If your Bosch mini-split is showing one of these, nothing is broken. dF in particular alarms people every winter. It is the normal defrost cycle, and the steam coming off the outdoor unit while it runs is normal too.

No code at all, just water?

A Bosch that is dripping or pooling water usually shows no error code, because nothing electrical has failed — the condensate simply has nowhere to go. That is a drain problem, not a fault code, and Bosch units have their own quirks there: the hose ships on the left and can be swapped to the right, the hole it came from has to be plugged, and heat pump outdoor units need a drain joint that often gets left in the box.

Those are covered step by step in cleaning the drain hose on a Bosch mini split.

Climate 5000 Gen 3 — the full error code table

These are the codes on current Bosch Climate 5000 Gen 3 single-zone systems — wall-mounted, four-way cassette and ducted — as published in the 2025 Bosch service manuals. The left column is the counted RUN-lamp pattern for units without a display.

Indoor and sensor faults (TIMER lamp off)

Of this group, two account for most calls:

• EL 01, the communication error, which is the single most reported Bosch code
• EH 03, the indoor fan speed error, which is very often just a blocked filter

Outdoor faults (TIMER lamp off)

Four of the six outdoor codes are sensors, and the pattern is worth noticing:

• EC 52, EC 53, EC 54 and EC 56 all share a five-flash RUN pattern, so the flash count alone cannot separate them — you need the display
• EC 51 shares that same five-flash pattern too, and it is a board fault rather than a sensor

Protection codes (TIMER lamp flashing)

Note two collisions in this group that make the display, not the lamp, the reliable source:

• PC 00 and PC 03 both flash seven times
• PC 01 and PC 02 are only one flash apart, at two and three

A single RUN flash with the TIMER lamp on, not flashing, is not a component fault at all. It is an indoor-unit mode conflict on a system sharing one outdoor unit, meaning one head is asking for heating while another asks for cooling.

What the EH, EL, EC and PC prefixes mean

Gen 3 codes become readable once you know the prefix, which is worth more than memorising the table.

Reading a Gen 3 code therefore goes in three steps:

1. Read the prefix to place the fault indoors, outdoors, on a link, or on a protection.
2. Read the number to name the exact component or limit.
3. Decide from the prefix alone whether it is a homeowner check or a service call.

EH and EC faults are usually a component that has failed or a wire that has come loose. PC codes are different in kind: nothing has necessarily broken yet, the system has stopped itself because a measured value went out of range. Resetting a PC code repeatedly is the one habit most likely to turn a protected system into a damaged one.

Climate 5000 Gen 2 and legacy single-zone — the full error code table

Older Bosch Climate 5000 wall-mounted single-split systems use a shorter set. This is the table Bosch prints in the installation manual, including the lamp pattern for each code.

Two of these trip people up regularly:

• EC on Gen 2 means low refrigerant. On Gen 3, EC is a prefix for outdoor-unit faults and means nothing on its own. Same two letters, completely different job.
• P3 on Gen 2 is a low-ambient-temperature lockout — the outdoor unit declining to run because it is too cold outside, which is protective rather than broken.

Multi-zone Bosch systems — outdoor codes and indoor codes differ

This is the section that is missing from most Bosch code pages, and it is the reason multi-zone diagnostics go wrong.

On a Bosch multi-zone Climate 5000, the outdoor unit’s display and the indoor head’s display report the same fault with different codes. Bosch prints both columns in the multi-split installation manual.

Indoor coil-outlet sensor faults are reported per head: F1 through F6 correspond to indoor units A through F, which is how a technician finds out which room’s head has the failed sensor without opening all of them.

Two consequences worth knowing before a service visit:

• A code in the F1–F6 range on a multi-zone outdoor board is naming a room, not a fault type
• The same letters on a Gen 2 single-zone system mean something completely different, because there is only one head to name

Two consequences worth knowing before a service visit:

• A code in the F1–F6 range on a multi-zone outdoor board is naming a room, not a fault type
• The same letters on a Gen 2 single-zone system mean something completely different, because there is only one head to name

The P6 problem — why P6 means two different things

Take the two rows for P6 above and read them together:

• On the outdoor board, P6 is an inverter module (IPM) malfunction.
• On the indoor display, P6 is what high-pressure (P1) and low-pressure (P2) protection look like.

So “my Bosch mini split shows P6” has two possible answers, and they lead to different repairs: a power-electronics fault, or a refrigerant-circuit pressure problem. P0 flips the same way — outdoor P0 is compressor top temperature, indoor P0 is the IPM fault.

When you call for service, say where you read the code. “P6 on the indoor head” and “P6 on the outdoor unit” are different jobs, and the difference decides what the technician brings.

EL 01, E1 and E2 — the communication error

The most common Bosch mini split fault across every generation is the indoor-to-outdoor communication error: E1 on Gen 2, EL 01 on Gen 3, E2 on a multi-zone outdoor board.

What triggers it

Bosch defines the Gen 3 trigger precisely: the indoor unit receives no feedback from the outdoor unit for 110 seconds, four times in a row. The listed causes are:

• Incorrect installation of the indoor-to-outdoor control wire
• Electromagnetic interference
• A faulty indoor or outdoor control board

What you can safely do

Power the system off at the breaker, wait two to three minutes, restore it, and see whether the code clears. That single reset is also the first step of Bosch’s own service procedure. Beyond that, the only homeowner-safe check is visual:

• Confirm the outdoor disconnect is closed and the breaker has not tripped
• Look for obvious damage to the conduit or cable run between the two units
• Note whether the code appeared after a storm or a power cut, which points at a latched fault rather than a failed part

What a technician does next

The published diagnostic measures DC voltage between terminals N/L2 and S at the outdoor unit, then traces the wiring between the terminal blocks and the boards. The reading itself is the diagnosis: a value fixed near zero, a value swinging between negative and positive, and a value stuck positive each send the technician down a different branch. That is a job with a meter and the covers off.

EEPROM parameter errors — EH 00, EH 0A, EC 51, E0 and F4

What the fault actually is

An EEPROM parameter error means the main chip on a control board is not getting a valid response from the memory chip that stores the unit’s settings. Bosch gives two causes: incorrect installation of the indoor-to-outdoor control wire or the line-voltage wiring, and a faulty PCB.

The same fault has a different name in each set:

• EH 00 or EH 0A — Gen 3, indoor board
• EC 51 — Gen 3, outdoor board
• E0 — Gen 2, indoor board
• F4 — Gen 2 indoor display, and what a multi-zone head shows when the outdoor board reports E0

The published procedure

1. Power off, wait two minutes, restart the unit.
2. If the error continues, replace the indoor main PCB.
3. If it still continues, replace the outdoor main PCB.

Only step 1 is a homeowner step. Steps 2 and 3 are board replacements. It is worth knowing that this fault frequently traces back to wiring rather than the board, which is why a technician should verify the control wiring before quoting you for two boards.

EL 0C and EC — refrigerant faults

EL 0C on Gen 3 is Bosch’s refrigerant-leak detection, and EC on Gen 2 is a low-refrigerant indication. Neither is a DIY repair. A mini-split does not consume refrigerant: if the charge is low, it has leaked, and topping it up without finding the leak means paying for the same repair again.

The symptoms that usually arrive with these codes are covered in more detail in our guides to a mini split not cooling, a mini split not heating and a mini split freezing up — ice on the line set is a classic low-charge signature.

Refrigerant handling is regulated. Recovering, charging and leak-testing a sealed system requires EPA Section 608 certification.

Inverter and IPM faults — PC 00, P0 and multi-zone P6

The IPM, or intelligent power module, is the block of power electronics that drives the compressor at variable speed. When it reports a fault, the system stops on purpose.

There is nothing safe to try here beyond one power cycle. These faults live on the high-voltage side, often on capacitors that hold charge after the power is off.

What not to do with an IPM code:

• Do not reset it repeatedly to get one more cooling cycle out of the system
• Do not open the outdoor electrical box to look, even with the disconnect pulled
• Do not accept a compressor quote before the drive board has been ruled out — PC 04 and PC 40 are drive faults, not compressor faults

Voltage, current and pressure protections

These codes mean a measured value left its allowed window. The system did the right thing by stopping.

Voltage codes

Confirm the breaker is the right size and fully on, and that nothing else large is sharing the circuit. A brown-out during a heatwave produces genuine under-voltage trips, and so does an undersized or shared circuit that was never right from the day it was installed.

Current and pressure codes

Make sure the outdoor unit can breathe. The usual causes are physical:

• Leaves, cottonwood or grass clippings packed into the coil
• A fence, deck or storage box built too close to the unit
• A snow drift or ice build-up in winter
• A dirty indoor coil starving the system of airflow on the other side

Our guide to an outdoor unit not running covers what to clear and how much space to leave.

Low ambient lockout

P3 on Gen 2 and LP on multi-zone are not failures. The outdoor unit is declining to run because it is too cold outside. If it appears in mild weather, that is worth a service call; in a cold snap it is the system behaving as designed.

Sensor codes — what T1, T2, T2B, T3, T4 and TP are

Half the Bosch code table is sensors, and the letter tells you which one.

The code wording is always “open circuit or short circuited”, which is the signature of a broken wire, a disconnected plug, or a thermistor that has failed. These are inexpensive parts, and it is worth asking whether the sensor was actually measured before a board is quoted.

Two things this table makes easy:

• Translating a Gen 2 code into its Gen 3 equivalent, and back, when a household has both generations
• Telling an indoor-side sensor fault from an outdoor-side one before anyone opens anything

Fan speed codes — EH 03, EC 07, E3, F5 and E8

A fan-speed fault means the board asked for a speed and the feedback did not match.

Indoor fan codes — EH 03 and E3

These have homeowner causes worth ruling out first:

• A filter so loaded that airflow has collapsed. See mini split filter cleaning
• A blocked or dirty blower wheel. See DIY coil cleaning
• Something physically fouling the louvre or the wheel
• Furniture or a curtain pushed against the head, throttling the return air

Outdoor fan codes — EC 07, F5 and E8

Check for debris, then stop. Outdoor fan motors and their capacitors are line-voltage components, and a capacitor holds charge after the disconnect is pulled.

The safe reset — what a power cycle can and cannot fix

One power cycle is a legitimate diagnostic step, and Bosch uses it as step one in its own published procedures.

How to do it properly

1. Turn the system off with the remote first.
2. Switch off the breaker or the outdoor disconnect.
3. Wait two to three minutes. The boards need time to discharge and clear state.
4. Restore power and let the unit start on its own.
5. Watch what the display does for the first few minutes.

What it can and cannot fix

A power cycle can clear a one-off glitch, a transient communication dropout, or a code that latched after a power outage. It cannot fix a failed sensor, a leak, a seized fan, or a board, and on protection codes it simply lets the system run back into the same limit.

If the code returns, that is your answer, and the next call is to a technician.

When to stop and call a licensed technician

Codes that go straight to a professional

Call for any of these, without a second reset:

• Any PC code on Gen 3, or any P code on Gen 2 and multi-zone
• EL 0C or EC, which are refrigerant codes
• Any EEPROM code that survives one power cycle
• Any code that returns within minutes of a reset
• Anything at all if you would have to open an electrical panel to go further

What to have ready when you call

• The exact code, written down as displayed
• Whether you read it on the indoor display or the outdoor board
• The outdoor unit’s model number from the data plate
• How many indoor heads are on the system
• Roughly when the fault started, and what the weather was doing

Our heat pump repair cost guide sets expectations on what the common repairs behind these codes tend to run.

Maintenance that prevents most Bosch codes

A significant share of the codes on this page — fan speed, coil sensors, high pressure, low airflow — start as maintenance that did not happen.

• Clean or replace the filters on the schedule the CL and F reminders are telling you about
• Keep the outdoor coil clear of leaves, cottonwood and grass clippings
• Keep the condensate drain line clear, especially in humid months
• Have the system serviced rather than waiting for a code
• Watch for the musty smell that signals a wet, dirty evaporator, which also affects indoor air quality

None of this prevents a board or an inverter failing. It does prevent the most common protection trips.

Bosch codes compared with other brands

If you are diagnosing a mixed system, or you replaced one brand with another, the letter grouping is similar across several inverter platforms but the meanings are not. Our brand hubs carry each manufacturer’s own published table:

• Gree error codes, the closest structural relative to the Bosch set
• Senville error codes
• Pioneer error codes
• MRCOOL error codes
• LG mini split error codes
• Daikin mini split error codes
• Mitsubishi mini split error codes
• Fujitsu mini split error codes

Or search every brand at once in the all-brand error code lookup, which now includes the Bosch mini-split error codes from this page.