A boiler that keeps cutting out is usually protecting itself. Low pressure, the thermostat and a frozen condensate pipe are things you can check. The rest need an engineer.
E133 on a Baxi means the boiler couldn't light. Baxi says it points to the gas supply, the ignition or a blocked condensate pipe. Here's how to check each one and reset it.
L2 on an Ideal boiler means ignition lockout: it tried to light and couldn't. Newer Logic Max boilers show the words Ignition Lockout instead. A frozen condensate pipe is one of the most common causes.
F28 and F29 mean your Vaillant can't light or keep its flame. F22 means the water pressure has dropped too low. Here's what to check, how to reset it and when to call an engineer.
EA means the boiler tried to light and couldn't detect a flame, so it locked itself out. Newer Greenstar boilers show it as 227. Often it's the gas supply or a frozen condensate pipe, and you can often sort it yourself.