Cause
Leaking heater matrix
The heater matrix inside the dashboard leaking coolant into the cabin. It is a small radiator in the ducting, so its leak arrives in the passenger compartment rather than under the vehicle.
The signs are distinctive and reach the driver first: a sweet smell, a greasy film on the inside of the windscreen that will not clear, and damp carpet in the passenger footwell. Coolant loss with no external leak and a misted screen is this before it is a head gasket. It also blocks, which is the other failure: heating that works on one side or not at all with a hot feed hose, from sediment in a system topped up with water. The labour is the cost — most are behind the dashboard — so confirm properly before committing.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
1 of the 1 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (1)
Codes where this is a likely explanation first, rather than merely a possible one.
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.
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