Control Unit Error - Connector Not Plugged Into The Gas Valve - Rinnai Q series Troubleshooting Manual

Check for 24 volts DC at gas valve.
Check across terminals 4 and 5 at plug X5 on the main
control board. See wiring diagram for your boiler for
terminal locations

Control unit error - Connector not plugged into the gas valve

or defect in the wiring harness to the gas valve.
In some cases an E03 is caused from a loose
connection on wires to the gas valve. This
faulty connection may be in the Molex plug
(X5) on the MCBA. Examine plug closely for
bayonets that may have backed out of plastic
casing.
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