Vaillant EcoMax Pro 18/28E (Fault Codes) Leave a Comment / Boiler Fault Codes, Vaillant Boiler / By Emergency Plumbers / May 3, 2012 May 3, 2020 / Boiler Fault Codes, Domestic Gas Boiler, EcoTEC Plus Error Codes, Vaillant, Vaillant EcoMax Pro 18/28E, Vaillant EcoTEC Pro, Vaillant F Codes, Vaillant Fault Codes Vaillant EcoMax Pro 18/28E Fault Code Possible Cause F.1 Lack of gas, a fault with the ignition or flue – may need to adjust the gas valve or replace a defective electrode lead. F.4 Ignition fault. F.5 The system has suffered a fault due to overheating. F.6 Your flow NTC has developed a fault. F.17 Check the polarity of your system. F.24 Pump-related faults – the pump could have failed, it may have over run or there could be an issue with the airlock