Grant Vortex Fault codes & diagnostics

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

Oil Oil 12-70 kW 2002-present
Download the Grant Vortex manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

Tap any card for details

10

Your boiler is struggling to vent exhaust gases properly when it starts up, which could lead to fumes building up in your home.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flue terminal
  • Burner seal
  • Draft stabilizer

Related codes

Full explanation for 10
12

Your boiler is allowing exhaust fumes to escape into your home, which is a serious safety concern that must be addressed immediately.

Emergency Engineer only £120-250

Parts commonly replaced

  • Burner gasket
  • Flue seal
  • Cleaning cover seal
Full explanation for 12
Lock-out

Your boiler has stopped working to protect itself and needs to be restarted, though it may take a few attempts to get it running again.

High DIY-safe £120-250

What to check first

  1. Check your external oil supply tank to ensure you have enough fuel and that any isolation valves are open.
  2. Locate the reset button on the boiler casing (or the burner unit) and press it once firmly.
  3. Wait for the boiler to attempt an ignition cycle; if it fails again, do not force the reset more than three times.

Parts commonly replaced

  • Photocell
  • Ignition electrodes
  • Fuel pump
  • Control box
Full explanation for Lock-out
Lock-out (Red neon)

Your boiler has stopped working because the flame inside failed to light or stay on.

High Engineer only £120-250

Parts commonly replaced

  • Photocell
  • Ignition electrodes
  • Oil nozzle
  • Control box
Full explanation for Lock-out (Red neon)
Status & diagnostic codes

29 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

15/26 Status Your boiler has detected a failure to ignite or a loss of flame during operation, meaning it cannot safely produce heat or hot water. 20.0 Status Your boiler has detected a failure in the ignition process, meaning it is currently unable to start up or stay lit to provide heat and hot water. 23.0 Status Your boiler has failed to ignite the flame, which means it cannot produce any heating or hot water until the issue is resolved. 26.0 Status Your boiler has detected an issue with the internal water pressure or flow, which has caused it to stop working to protect itself. 26/36 Diagnostic Your boiler has detected a failure to ignite or a loss of flame, meaning it cannot produce heat or hot water reliably. 31.5 Status Your boiler has detected a communication error between its main control board and the internal display unit, preventing it from operating correctly. 36.0 Status Your boiler has detected a communication error between the main control board and the internal electronic components, preventing it from firing up. 36/46 Diagnostic Your boiler has failed to ignite because the burner has reached its maximum number of failed start attempts, likely due to a fuel or air supply issue. 41.5 Status Your boiler has detected an issue with the water pressure level, which has triggered a safety shutdown to prevent damage to the system. 46.0 Status Your boiler has detected that the water flow through the heating system is too low or blocked, preventing it from heating your home safely. 46/58 Diagnostic Your boiler's control system has detected a potential communication error or a sensor fault that is preventing it from firing up correctly. 52.0 Status Your boiler has detected a problem with the burner's ability to ignite or stay lit, causing it to stop heating. 58.0 Status Your boiler has detected an issue with the internal communication between its control components, which has caused it to stop working for safety reasons. 58/70 Diagnostic Your boiler has detected a failure in its internal communication or electronic control system, meaning it cannot safely operate or regulate itself. 64.0 Status Your boiler has detected an issue with the internal electronics or a communication error that is preventing it from operating correctly. 70.0 Status Your boiler has detected that the water temperature has risen too high and it has automatically shut itself down to prevent any damage. GE45/90 Diagnostic Your boiler has detected an issue with the physical alignment or connection of the exhaust flue pipe exiting the unit. GEB90 Diagnostic Your boiler is flagging an issue with the mounting bracket used for an external flue installation, often indicating that the flue pipe is not securely fixed or supported correctly. GEB200 Diagnostic Your boiler's wall mounting bracket has shifted or extended beyond its intended position, which could cause the unit to become unstable. GK90 Diagnostic Your boiler is failing to start up because the ignition system, which is responsible for lighting the fuel to produce heat, is not functioning correctly. GK90S Diagnostic Your boiler's internal electrical start-up system has detected a short circuit, preventing the unit from igniting and providing heating or hot water. GK200 Diagnostic Your boiler is failing to light the burner because it is struggling to initiate the start-up sequence. GK200S Diagnostic Your boiler's ignition system is experiencing an electrical fault, meaning the boiler cannot safely start up to provide heat or hot water. GTH90 Diagnostic Your boiler has detected that exhaust gases are not escaping properly, likely because the flue outside is obstructed or damaged. GTH200 Diagnostic Your boiler has detected that exhaust gases are being blown back into the unit, likely due to external weather conditions or a blockage near the flue terminal. GTV90 Diagnostic Your boiler's outdoor exhaust vent has likely become blocked, damaged, or disconnected, preventing the safe escape of exhaust gases. GTV200 Diagnostic Your boiler is struggling to breathe properly because the outdoor air intake or exhaust pipe on your roof is likely blocked, damaged, or obstructed by debris. GWB90 Diagnostic This code indicates that the mounting bracket securing your boiler to the wall is either loose, damaged, or incorrectly installed, which could cause the unit to become unstable. GWB200 Diagnostic This code indicates that the mounting bracket securing your boiler to the wall is not correctly attached or positioned.
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