Montague Oven Error Code Er03: Invalid State on Main Board
Er03 on the Montague V136EO-4I convection oven means the main board has encountered an invalid state. The manual gives one remedy: clear the code by turning off power to the oven. If Er03 returns right away or often, a technician should look at it.
Low: the manual lists a power-off clear only, with no service referral.
What does Montague error code Er03 mean?
Every electronic control tracks what step it is in. If the main board finds itself in a state that should not be possible, it reports it rather than guessing. That is what Er03 is: the manual says the main board has encountered an invalid state, and the code is shown on the oven control display. It is the simplest entry in the oven list. The manual names one cause, the invalid state, and a single action, which is to clear the code by turning off power to the oven. It does not add a call to a service provider for this code, in contrast to Er01, Er02, Er04 and Er05, and it does not name any part to check. It also does not say what the oven does while the code is on screen, so we do not claim that heating stops. A power cycle gives the board a clean start. Whether a one-time invalid state is a harmless glitch or an early sign of a failing board is not something the manual tells us.
Affected models and control systems
Montague Legend electric range model V136EO-4I, convection oven only. Er03 is listed under Service, Error Codes on printed p. 12.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- Er03 on the oven control display
- Controls that stop responding as expected
- An oven that behaves normally again after power is cut
Possible causes
Listed in Montague's documentation
- Invalid state on the main board
Other likely causes — what usually sits behind error code Er03 on this control. A technician confirms which one it is before any part is replaced.
- A power surge or brownout that interrupted the board mid-operation
- A voltage dip when a large load started elsewhere on the same circuit
- Keys pressed in a rapid sequence that confused the control
Safe checks before calling for service
- Turn off power to the oven, as the manual says, and wait about a minute.
- Turn power back on and start a normal cycle.
- Watch whether Er03 comes back and how soon after the restart.
- If it returns, note the time, what you were doing, and whether any other code showed first.
How a technician diagnoses error code Er03
- Read the code and ask how often it appears and what the oven was doing.
- Check the supply voltage at the oven for dips under load.
- Check the connectors to the main board for seating, with power isolated.
- Look for a pattern of Er03 with other codes, which would point at the board or at noise.
- Replace the main board only if Er03 repeats after the supply and connections have been proven good.
- Supply and board checks on an oven mean working near 208 to 240 V terminals, which is a technician's job.
- A repeating Er03 needs more than a reset: someone has to separate supply problems from a failing board.
- The board holds the oven's calibration, so swapping it blindly can leave the oven out of tune.
How error code Er03 differs from similar codes
Er03 is the only Er code in this oven list that the manual clears with a power-off alone. Er01 also starts with a power-off but adds checks.
Technical reference
- Document
- Montague Legend Electric Range, Operation Manual, Installation/Operations
- Edition
- No revision printed (file name: Final-Submission; listed on montaguecompany.com/manuals in 2026)
- Models / control
- Legend Electric Range model V136EO-4I (convection oven only)
- Section
- Service, Error Codes, printed p. 12
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Montague range error codes
Is Er03 serious?
The manual treats it as a clear-by-power-off code, with no service call listed. If it keeps coming back, treat it as more than a one-off.
What does invalid state mean?
The main board found itself in a condition it is not designed to be in, so it reports Er03.
How long should I leave the power off?
The manual does not give a time, only to turn off power to the oven. A minute is a reasonable pause.
Need help with Montague error code Er03?
A technician confirms the cause on site and gives you the price in writing before any work starts.