Error Handling

Error Status Query

Errors are queried using ReadByIdentifier (SID=0xB2) with Identifier=0x23.

Request:

7F 06 B2 23 17 46 40 03
│  │  │  │  │  │  └──┴─ Function ID (0x0340 = CombiGas)
│  │  │  │  └──┴─────── Supplier ID (0x4617 = Truma)
│  │  │  └───────────── Identifier (0x23 = ErrorStatus)
│  │  └──────────────── SID (0xB2 = ReadByIdentifier)
│  └─────────────────── PCI (0x06 = 6 bytes)
└────────────────────── NAD (0x7F = Broadcast)

Error Response Format

No Error:

01 06 F2 02 00 00 00 00
         │  │  │
         │  │  └─────── Error Code = 0 (none)
         │  └────────── Error Class = 0 (OK)
         └───────────── Format = 0x02

With Error (example W621H):

01 06 F2 02 06 15 3F F9
         │  │  │  └──┴─ Additional data (meaning unknown)
         │  │  └─────── Error Code = 0x15 (21 decimal)
         │  └────────── Error Class = 0x06 (6)
         └───────────── Format = 0x02

Error Code Decoding

The error code displayed on the Truma panel is composed from class and code:

Display Code = (Class * 100) + Code

Bytes	Class	Code	Display
`06 15`	6	21	621
`00 00`	0	0	OK

Error Classification

Format	Class	Type
0x01	0x00	OK
0x01	0x01-0x0F	Warning (W)
0x01	0x10+	Error (E)
0x02	0x00	OK
0x02	0x01-0x04	Warning (W)
0x02	0x05+	Error (E)

Note: The actual W/E prefix on the display may follow Truma-specific rules that differ from this classification.

Suffix

H = Heater (Combi)
A = Aircon (Aventa/Saphir)

Polling Interval

The master polls ErrorStatus approximately every 800ms during normal operation.

Common Error Codes

Combi Gas — Codes before April 2018

These codes apply to Combi 2, Combi 4, and Combi 6 (including E variants) with older electronics (range #17–#255):

Code	Meaning	Solution
W 17 H	Summer mode with empty boiler	Turn off heating, let cool down, fill boiler with water
W 18 H	Hot air outlets or recirculation blocked	Check all 4 outlets, remove blockage
E 21 H	Room temperature sensor or cable defective	Check cable; NTC resistance: 15°C = 16.2 kΩ, 20°C = 12.6 kΩ, 25°C = 10.0 kΩ
W 24 H	Imminent undervoltage < 10.4 V	Charge battery
E 28 H	Current to control panel too high	Check/replace control panel cable and panel
E 29 H	FrostControl heating element short circuit	Disconnect from electronics, replace element
E 41 H	Electronics locked (overtemperature > 215°C)	Check heat exchanger and boiler for frost damage; unlock with diagnostic tool
E 42 H	Window above chimney open (window contact)	Close window; if persistent, check contact
E 43 H	Overvoltage > 16.4 V	Check battery charger, solar controller
E 44 H	Undervoltage < 10.0 V	Charge or replace battery
W 45 H	No 230 V supply / fuse defective / overheating protection	Restore 230 V, replace fuse — Combi E / eco plus / comfort plus only
E 46 H	Circulation motor, control panel or wiring harness defective	Replace motor, panel or wiring harness
E 60 H	Voltage fluctuations	Check 12 V supply under load
E 112 H	Flame not detected / faulty ground connection	Check gas supply, grounding, igniter, solenoid valve, exhaust path
E 113 H	Ionization voltage in standby	Check solenoid valve (stuck open)
E 116/117 H	AC voltage components in supply voltage	Check charger or solar system as interference source
E 118 H	Combustion air motor — speed too low	Replace motor kit
E 119 H	Combustion air motor — speed too high	Replace motor kit
E 121 H	Flame unstable during operation	Check gas supply, grounding, solenoid valve
E 122 H	Gas supply interrupted / air/exhaust path blocked	Check chimney openings for snow, ice, insect nests; check gas regulator
E 148 H	Electronics locked (combustion air sensor overtemp.)	Like E 41 H — unlock with diagnostic tool
E 149/150 H	Air/water temperature switch overtemperature	Check heat exchanger and boiler for frost damage
E 202 H	Flame not detected (2nd ignition cycle)	Like E 112 H
E 203 H	Ionization voltage in standby (2nd cycle)	Check/replace solenoid valve
E 211 H	Flame unstable (2nd ignition cycle)	Like E 121 H
E 212 H	Gas supply interrupted (2nd cycle) / electronics defective	Like E 122 H; if electronics fault contact Truma service
E 238 H	Electronics locked (combustion air overtemp.)	Like E 41/148 H
E 239/240 H	Overtemperature fault	Check heat exchanger, boiler, thermostat plate
E 255 H	No 12 V / no connection heater–control panel	Ensure 12 V supply, check cables, inspect connectors for corrosion

Pattern: Codes in range 1xx relate to first ignition cycle, codes in 2xx to second ignition cycle of the same fault type (e.g., E 112 → E 202, E 121 → E 211).

Combi Gas — Codes from April 2018

New electronics generation uses three-digit codes in range 255–731, systematically grouped by function. Applies to Combi 4 and Combi 6 (including Combi E variants) from build date 04/2018:

Code	Meaning	Solution
E 255 H	No 12 V / no connection heater–control panel	Check 12 V supply and cable connection
E 301/417 H	Overvoltage > 16.4 V	Check charger, solar controller
E 302/418 H	Undervoltage < 10.0 V	Charge or replace battery
W 303/411 H	Imminent undervoltage < 10.4 V	Charge battery
E 304 H	Re-ignition	Informational — no action required
E 305 H	Electronics fault	Check 12 V supply; replace PCB
E 401 H	Summer mode with empty boiler	Turn off heating, cool down, fill with water
E 402 H	Hot air temperature exceeded (pipes blocked)	All 4 hot air hoses connected? Outlets clear?
E 407 H	No 230 V supply / fuse defective	Restore 230 V — Combi E models only
E 408 H	No gas supply in mix mode	Check gas supply; electric heating continues
E 412 H	Window above chimney open	Close window
E 413/414 H	Electronics fault	Replace PCB
E 419 H	Overheating protection triggered	Reset overheating protection
E 420 H	230 V overvoltage	Check 230 V supply and electronics
E 421 H	Electronics fault	Replace PCB
E 501 H	Electronics fault	Replace PCB
E 502/503 H	Heater too hot / combustion air sensor fault	Check thermostat plate and heat exchanger
E 504 H	Combustion air temperature sensor out of tolerance	Check thermostat plate and wiring harness
E 506 H	Combustion air motor speed out of tolerance	Replace motor kit
E 507 H	Gas supply interrupted	Check gas bottle, valves, regulator, exhaust path — most common fault
E 508 H	Ionization voltage in standby	Check solenoid valve (stuck open)
E 509 H	Igniter current too high	Replace igniter
E 510 H	Solenoid valves incorrectly controlled	Replace wiring harness/PCB
E 511 H	Electronics fault	Replace PCB
E 512 H	Air temperature switch triggered by overheating	Check connector contacts X1, heat exchanger
E 513 H	Water temperature switch triggered by overheating	Check water temp. monitoring wiring harness
E 514 H	Power interruption during operation	Check 12 V; replace temp. monitoring wiring harness
E 515/516/517 H	Gas supply interrupted (variants)	Like E 507 H
E 520/521 H	Electronics fault	Replace PCB
E 522 H	Combustion air motor speed out of tolerance	Replace motor kit
E 523 H	Igniter current too high	Replace igniter
E 524 H	Combustion air motor short circuit	Check motor and cable
E 525/526 H	Combustion air motor current too high/low	Check/replace motor
E 527 H	Igniter current too low	Replace igniter
E 528–534 H	Solenoid valve coil currents too high (various)	Replace wiring harness
E 601/602 H	Electronics fault	Replace PCB
E 603 H	Electronics locked (overtemperature)	Unlock with diagnostic tool
E 605 H	Overtemperature fault	Check heat exchanger and boiler
E 607 H	Max. fault resets reached (> 4 in 15 min.)	Wait 15 minutes, do not turn off panel
E 608 H	CP Plus initialization doesn’t match heater	Re-initialize CP Plus
E 617 H	Electronics locked (combustion air > 215°C)	Unlock with diagnostic tool
E 619 H	Water temperature sensor out of tolerance	Replace temp. monitoring wiring harness
E 620 H	Air temperature sensor out of tolerance	Check temp. monitoring wiring harness
E 621 H	Room temperature sensor defective	Check cable and NTC resistance
E 622 H	Control panel or cable defective	Replace cable/panel
E 623 H	Heater under voltage at power-on	Turn off and back on
E 624 H	FrostControl heating element short circuit	Replace element
E 627/628 H	Circulation motor current too high/low	Check/replace motor
E 632 H	230 V water temperature switch triggered	Reset switch
E 700–731 H	Various electronics faults	Replace PCB with diagnostic tool

Functional grouping: 3xx = voltage issues, 4xx = operating state faults, 5xx = gas/combustion faults, 6xx = sensor faults and repeat locks, 7xx = electronics faults.

Combi Diesel — Separate Code Series

Combi D (D4, D6 and DE variants) uses a separate numbering range #111–#423 plus newer 5xx codes:

Code	Meaning	Solution
E 111 H	Room temperature sensor defective	Check NTC resistance values
E 122 H	Fuel shortage (tank empty/low/tilted)	Fill tank, bleed fuel line
E 131 H	No connection heater–control panel	Check connection and cables
E 132 H	FrostControl heating element short circuit	Replace element
E 150 H	Hot air temperature exceeded	Check all 4 hot air hoses and outlets
E 151 H	Water temperature exceeded in winter mode	Turn off heating, cool down, fill boiler
E 152 H	Water temperature exceeded in summer mode	Like E 151 H
E 160 H	Undervoltage < 10.2 V	Charge battery; start vehicle engine (glow plug needs ~4 min. high current)
E 161 H	Overvoltage > 16.4 V	Check charger
E 162 H	Window above chimney open	Close window
E 164 H	No 230 V / fuse defective / overheating protection	Restore 230 V, replace fuse
W 170 H	Imminent undervoltage < 11.5 V	Reduce consumers, charge battery
E 423 H	Initial fill pending	Set temperature to 30°C for activation
E 551 H	Glow plug has insufficient energy absorption	Replace glow plug with cover (special tool required) — not officially documented
E 563 H	Combustion air motor current implausible	Replace motor or PCB; check exhaust hose clamp

Important: Undervoltage threshold for diesel is 11.5 V (vs. 10.4 V for gas models) as glow plug draws significantly more current during diesel start.

Air Conditioning (Aventa and Saphir) — Five Common Codes

All CP-Plus-compatible air conditioners use the same set of just five error codes with suffix “A”:

Code	Meaning	Solution
# 1 A	Room temperature sensor failed (short/break)	Contact Truma service
# 2 A	Internal ice sensor failed	Check and clean/replace filter
# 4 A	External ice sensor failed (if present)	Keep roof air in-/outlets clear
# 8 A	IR receiver disconnected or cable break	Contact Truma service
# 17 A	Voltage drop in 230 V supply	Check 230 V power supply

Most Common Faults in Practice

Based on community experience, the most frequent error codes are:

E 507 H (and variants 515–517) — Gas supply issues
- Empty gas bottle
- Insect nests in burner or exhaust pipe
- Iced pressure regulator (use propane, not butane in cold weather)
E 255 H — Power/connection issues
- Check 12 V battery and connections
- Inspect connectors for corrosion
E 112/122/202/212 H (older generation) — Gas supply and ignition
- Check ground connection to chassis
- Inspect gas supply path
- Check chimney for blockages