No Heat plus P2457 code

I had low cabin heat for a period of time and suddenly went to no heat condition at the beginning of this week. Next day the P2457 engine code was thrown.

Is there a way to definitively tell if it’s the heater core or a stuck open thermostat?

Thanks!

If I end up needing a core, does anyone have a good source for a new one?

Sounds like a clogged heater core (common) and not letting coolant flow through to the egr cooler. While the core isn't relatively difficult to change, I would definitely try back flushing it first. Take the hoses off that go to the heater core. Then flush with a garden hose on one side and then the other. You will see the clog pop out in large pieces and then smaller ones. Keep doing until nothing flows but clear water. It's usually easier to take the hoses off of the engine and use the hoses (still connected to the heater core) to flush it out. Rather than getting to the firewall and just sticking a nozzle into the core at an awkward angle. If for some reason flushing doesn't fix it, 1stvw parts is a great online VW parts supplier. Good luck!

So... I'm thinking that this, might actually be a thermostat issue. The top rad hose on the upper right (as you stand in front of the car) is warm and the lower left hose is cold. Is this pretty much a definitive conclusion?

I take it back. It's the heater core. Top line to the core is cold and bottom is hot when fan is on. When fan is off, both eventually become the same temperature.

One more question.

What is the temperature control dial connected to? (I've got a Trendline, no climatronic control)

Hey Dieseline,

Having a similar issue. Was it the thermostat or the heater core?

Thanks