P2029: Fuel Fired Heater Disabled
What to do
The car drives normally; you may notice slower cabin warm-up in cold weather. Often not a fault at all — the heater declines to run when fuel is low, at high altitude, or when the battery is weak. If you keep the tank well filled and it still will not run, then it is worth investigating.
What this code means
The auxiliary fuel-fired heater has been switched off by the control module. This device exists because of an inconvenient consequence of diesel efficiency: a modern diesel converts so little of its fuel into waste heat that on a cold day it may never warm the cabin properly, and may take a long time to reach its own operating temperature. A small burner running on the vehicle's own fuel makes up the difference.
"Disabled" usually means the module decided not to run it, rather than that anything is broken, and the conditions it declines under are ordinary: fuel level below a threshold, so the heater cannot empty the tank; altitude too high for reliable combustion; battery voltage too low to support the glow element; or the engine already warm enough not to need it.
So this code frequently records correct behaviour. Where it is a fault, a sooted-up burner from repeated short cycles is the usual reason, and running the heater for a full cycle occasionally is what prevents that.
Likely causes
Start here
- Fuel level below the heater threshold · easy
- Low system voltage · moderate
- Soot build-up in the heater burner · moderate
Less common
- Operation inhibited at high altitude · easy
- Faulty fuel fired heater · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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