Rational SCC combi oven Error Codes
Applies to: SCC series combi ovens. Compiled and paraphrased from Rational's own SCC Service Reference, edition 01-2006, published by Rational at service.rational-ag.com and mirrored by a distributor, supplemented by Rational SelfCookingCenter whitefficiency (SCC WE) service documentation for the later generation. TWO CONFLICTS ARE PUBLISHED RATHER THAN RESOLVED, because both readings appear in Rational-related documentation for different generations: Service 10, where Rational's own reference says the SC pump is without function while the widely circulated list says the opposite, and Service 21, where the 2006 reference says a clima control micro switch and later SCC WE documentation says a control board monitoring error. A widely reproduced third-party compilation of these codes exists and is deliberately NOT used here, because it is assembled by a parts distributor and credits a forum contributor in its own text. Codes and their handling vary by model generation (SCC, SCC WE, iCombi); confirm the software version before ordering parts. NOT YET COVERED: the same Rational reference carries a separate Combi Master (CM) fault set, E1 through E24 with its own meanings, which is a different control and is not reproduced here. Table last updated Aug 15, 2026.
How to read the codes
Rational SelfCookingCenter units display faults as Service plus a number on the control panel. Record the exact Service number and what the oven was doing (cooking mode, CleanJet cycle, startup) before calling; Rational service runs through certified service partners, and the code plus context often lets them arrive with the right part.
The codes
| Code | Meaning | Likely causes | Operator-safe steps | Technician work |
|---|---|---|---|---|
| Service 10 | Self-clean water not pumped out | Rational's own service reference gives this as the SC pump WITHOUT FUNCTION. The list that circulates most widely online gives the opposite, a pump seeing a high water level with the remedy to drain its hose. Both appear in Rational-related documentation for different generations, so this table states the conflict rather than choosing: on an older SCC treat it as a dead or blocked pump, and check the hose before assuming failure. SC pump not working or its tubing blocked or restricted | Record the code; check for visible drain blockage | SC pump and tubing service |
| Service 11 | Water metering sensor over-reading during steam generator fill | CDS sensor calibration, air break valve not closing during fill, level electrode or supply leak | Confirm water supply pressure; record the code | CDS sensor, air break valve, and level electrode diagnosis |
| Service 21 | Voltage or current monitoring error on the main control board | CONFLICT WORTH KNOWING BEFORE ORDERING A PART. Rational's SCC Service Reference, edition 01-2006, gives Service 21 as a faulty clima control MICRO SWITCH. Later SCC WE documentation gives the same code as a voltage or current monitoring error on the main control board. Those are different parts at very different prices, and which one applies depends on the generation of the unit. Check the software version before ordering. Control board supply voltages or monitored circuits out of range | Record the code for the technician | Control board electrical diagnosis |
| Service 25 | No water flow detected during CleanJet | Water supply off or weak, moistening valve or nozzle blocked, CDS sensor fault; the board watches for the fan motor load to rise when water injects | Confirm the water supply is on and pressure is normal, then retry | CleanJet water path and sensor diagnosis |
| Service 28 | Steam generator over temperature | Steam generator thermocouple B5 above 356 F, very commonly scale buildup; the indicator clears once temperature falls below about 230 F | Run descale and care cycles on schedule with approved tabs | Steam generator descale and thermocouple service |
| Service 29 | Control board over temperature | PCB above 185 F: blocked ventilation, dirty air filter, cooling fan failure | Clear ventilation openings and clean accessible filters | Cooling fan and board service |
| Service 30 | Running in emergency humidity control | A humidity measurement fault; the oven keeps cooking in a fallback mode | Finish service and schedule repair; food results may vary | Humidity sensing system diagnosis |
| Service 40 | Care Control fault | Care tab and water dosing into the steam generator not completing; wrong or missing tabs | Use only approved care tabs, loaded correctly; retry once | Care system pump and dosing service |
| Service 12 | CDS sensor giving no output signal | The conductivity and flow sensor is not reporting. Rational's reference pairs this with low water pressure or a blocked signal path | Check the water supply is on and the isolating valve fully open before calling; low incoming pressure presents identically to a failed sensor | CDS sensor and its wiring, then incoming water pressure at the unit |
| Service 13 | Steam generator not refilling during steam mode | Rational's remedy names the level electrode directly: the control is not seeing the fill it asked for | Nothing an operator can safely resolve. Record the code exactly, including any decimal, and call. | Level electrode and its 0-1 signal to the PCB |
| Service 14 | Level electrode not recognising water | Water conductivity too low for the electrode to register. This is the one fault on the list caused by water that is TOO clean: fully softened or reverse-osmosis water can stop conducting enough for the probe to see it | If the site has recently changed water treatment, say so when you call. It is the likeliest cause and it is not a broken part | Level electrode and water conductivity. Rational notes osmosis water specifically |
| Service 16 | Software version too old for the function requested | Rational's note is that from software 01-07-09 onward the new version must be flashed first | Nothing an operator can safely resolve. Record the code exactly, including any decimal, and call. | Flash current software before diagnosing further |
| Service 17 | External EEPROM faulty | Stored settings cannot be read or written. Later SCC WE documentation describes this position as an SD card fault instead, so confirm against the generation in front of you | Nothing an operator can safely resolve. Record the code exactly, including any decimal, and call. | EEPROM or SD card depending on generation |
| Service 23 | Solid state relay short circuit, steam | The steam SSR has failed closed. A relay stuck closed means uncontrolled heating, which is why this is a stop-now fault rather than a degraded-operation one | Stop using the oven and call. Do not attempt to keep cooking on hot air only | Steam SSR: repair or replace |
| Service 24 | Solid state relay short circuit, hot air | The hot air SSR has failed closed. Same reasoning as Service 23 | Stop using the oven and call | Hot air SSR: repair or replace |
| Service 26 | Drain valve permanently closed | The valve is not opening at all, so nothing drains | Nothing an operator can safely resolve. Record the code exactly, including any decimal, and call. | Drain valve assembly |
| Service 27 | Drain valve will not close, CleanJet unavailable | The opposite failure to Service 26, and it disables cleaning rather than cooking | Rational’s published recovery is to start the rinse or abort program | Drain valve assembly and its initialisation |
| Service 31.x | Core probe faulty, with the digit naming which probe | The decimal is a BITMASK, not a probe number, and this is where readings get misread. 31.1 is the shaft probe, 31.2 the fifth probe near the shaft, 31.4 the fourth, 31.8 the third, 31.16 the second, 31.32 the first probe in the tip. Combinations ADD: a faulty fourth and third probe displays as 31.12 | Write the full code including the decimal. It tells the technician which probe before they open anything | Add the values to decode multiple failures. Repair or replace the identified probe |
| Service 32.x | Ignition box faulty | 32.0 is the top ignition box, 32.1 the bottom (floor models only), 32.2 both | Nothing an operator can safely resolve. Record the code exactly, including any decimal, and call. | Change the ignition box the digit identifies |
| Service 33.x | Repeated ignition resets without success | Rational's own wording is four resets without function. The box is being asked to light and failing each time | Nothing an operator can safely resolve. Record the code exactly, including any decimal, and call. | Ignition wiring, ignition box gas valve and supply |
| Service 34.x | Bus signal error, with the digit naming the device | Another bitmask: 1 is the I/O board, 2 the bottom motor, 4 the top motor, 8 the top ignition box, 16 the bottom ignition box, and combinations add. Note the later SCC WE documentation numbers these differently, so confirm the generation | Record the full code with its decimal | Bus cable plug and cable connections before replacing anything |
| Service 35 | Bus signal cannot be processed because the UltraVent is disconnected | A disconnected ventless hood, not an oven fault | Check the UltraVent is connected and powered | Reconnect the UltraVent |
| Service 36 / Service 37 | Differential pressure sensor P1 faulty or out of range | 36 is a defective sensor, 37 is a sensor reading outside its expected range, which Rational attributes to hose connections rather than the sensor itself | Nothing an operator can safely resolve. Record the code exactly, including any decimal, and call. | For 37 check hose connections before replacing the sensor |
If this needs a combi oven technician
4 companies in this directory name Rational on their own site: that page shows who has been phone-confirmed, who publishes 24/7 cover, and what each puts in writing. Start there if the brand matters more than the city.
Two questions worth reading before you ring anyone: what to do first when a code appears and how to tell whether it is yours to fix.
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Related: the PM checklist that prevents the most common codes outright, and the operator guides for symptom-first diagnosis.
Not sure this is the right make? The lookup by code shows every make that uses a given code, and flags the ones that mean different things depending on the machine in front of you.