P0401 - EGR Code, 2010 Prius, Need Help

The whole egr circuit needs to be cleaned stem to stern.

If you’re not sure what the mechanic cleaned, ask him and if he can’t remember, probably best to tackle the whole circuit.

Other things to do:

• Keep an eye on the engine coolant level as you might be at the tip of the head gasket iceberg
• Install an oil catch can to catch the PCV vapors

Good luck and keep us posted .

 

"the tip of the head gasket iceberg"

Impending doom - unless you don't believe in global warming!

 

The valve is relatively inexpensive part to replace, I would clean the EGR circuit and replace the valve

 

EGR valve? It's over $200.

EGR System for 2010 Toyota Prius | McGeorge Toyota Parts

Very likely he did not completely clean the EGR circuit: it involves everything from the connection to the exhaust manifold to the intake ports. You need to remove the wipers, motor/linkage cowl, intake air snorkel and filter box , throttle body, intake manifold (and thoroughly clean it: it has egr passages), and (obviously) the EGR tube, valve and pipe (see link).

Some boilerplate:

The simplest way to see where you're at, is to check the degree of carbon build up in the EGR tube, a stainless steel connecting pipe between the EGR valve and intake manifold. Watch @NutzAboutBolts video #16 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

Two or three other videos linked there too, for the full cleaning of the intake manifold, full EGR clean, and Oil Catch Can install.

Good thread:

EGR & Intake Manifold Clean Results | PriusChat

Another:

Oil Catch Can, Eliminate that knock! | PriusChat

Somewhat tools worth having:

E8 Torx socket (mandatory)
E6 Torx socket (optional, but good to have, to remove the throttle body studs from intake manifold)
3/8" ratchet wrench, regular and long handle, flex head, you can never have enough
1/4" ratchet wrench, or 3/8" to 1/4" reducer
Ratchet extensions: you can never have enough
Long needle nose piers, straight and bent tip
Ratcheting 12mm box wrench (optional, but makes disconnection of the EGR cooler from exhaust easier)
Torque wrench (3/8" and 1/4" both good to have)
Floor jack and safety stands (or ramps): basically some method to raise front, if you need to take underpanel off, which you may need to, both for access and to recover dropped items.

Repair Manual info attached:

 

It's probably close to $200. I should say relatively cheap compared to other repairs on this Turd Gen

 

Salvage yard was 1/4 of the OEM list.

Help keep useable parts functioning and out of the recycle stream.

 

I got a very nice one (barely even had to clean it) off eBay for USD140.00 shipped.

 

4 years ago I bought a salvage yard cooler and valve for $100.

Slight cleaning required .

But they work just as well as new.

 

To buy new and pay a mechanic is extremely costly.

The components in your car are hopefully viable once cleaned, and if at all possible I would DIY the cleaning. You really need to clean everything between the exhaust manifold connection and the engine intake ports; that involves the intake manifold as well. Doing it yourself, and just cleaning what you have, you get through this with next to zero expense.

Have a look at the @NutzAboutBolts video links I mentioned above, both the EGR and Intake Manifold cleaning. And for sure read through the linked threads. Lots of info in there.