Grant Vortex Pro Fault codes & diagnostics

4 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

OilSystem OilNatural Gas 26-35 kW present

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Grant Vortex Pro faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

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10

Your boiler is struggling to push smoke and exhaust gases out properly during startup, which can lead to fumes leaking into your home.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue seals
  • Burner gasket
  • Chimney liner
Full explanation for 10
12

Your boiler is detecting that exhaust fumes are leaking inside or near the unit instead of going properly up the chimney flue.

Emergency Engineer only £120-250

Parts commonly replaced

  • Combustion chamber door seal
  • Flue seal gaskets
  • Burner gasket
Full explanation for 12
Lock-out

Your boiler has stopped working as a safety precaution because it failed to ignite, so it is currently waiting for a manual reset.

High DIY-safe £120-250

What to check first

  1. Ensure your oil tank has sufficient fuel and the supply valve is open
  2. Locate the red reset button on the burner casing and press it firmly once
  3. Wait for the boiler to attempt an ignition sequence; if it locks out again, do not force it

Parts commonly replaced

  • Photocell
  • Ignition electrodes
  • Oil nozzle
  • Control box

Related codes

Full explanation for Lock-out
Overheat

Your boiler has detected that it is getting dangerously hot and has shut itself down to prevent any internal damage.

High Engineer only £150-350

Parts commonly replaced

  • High limit thermostat
  • Circulating pump
  • Heat exchanger
Full explanation for Overheat