The meaning of P1403 & P1404 Additional heat command fault codes

[hairgoneJohn]

As an aside to another thread that I've started , for those seeking the meaning of the P1403/1404 codes I've just found an interesting thread. Look at the post near the bottom with the wiring diagram

https://citroenc3owners.com/viewtopic.p ... tent=zid-1

It would appear that there are electric heaters within the heater matrix that provide instant cabin heat in cold weather.

[Paul-R]

Electric heaters in the heating system are not a new thing. They used to be ordinary engine glow plugs (and maybe still are) and are there to provide warmth as soon as possible in cold weather on diesel engines because of their long warm up times. I had them on my 2003 Citroen C5.

This is now more important on Euro 6 engines as they are required to get to operating temperature as soon as possible so that emissions can then be controlled.

[hairgoneJohn]

These are not glow plugs. They are heaters in the heater matrix to warm the cabin, not the fuel.

[Paul-R]

Yes I know. I'm saying that when this electric heating system was first applied to the cabin heating I read that ordinary glow plugs were used. I didn't mention anything about the fuel.

[Rhothgar]

These are not glow plugs. They are heaters in the heater matrix to warm the cabin, not the fuel.

It might help if you actually told people what vehicle you are referring to rather than leaving them to go digging for what you are referring to.

Yes. They did used to be glow plugs on proper old school Citroens). The DTC codes are common amongst most makes and models of cars. Those different makes and models of cars all may well have different actuation systems to achieve the same effect.