The dreaded P0401 and rattle at power mode in throttle.

Aloha everyone, I've been reading posts on here since I got our 2010 Prius and more recently as it rolled over 175k and seems like a bunch of issues popped up at once.

I'm dealing with a couple issues. One the check engine light came on in first month we had the car. Code is P0401. Since it was running fine I cleared it and figured like most cars it'll be back soon if it's not an error or old code. (We also had to replace the 12v battery around this time so I chalked it up to possibly getting triggered from this) Well it stayed off for a long time like 4-5 months. Only recently have we had some issues that I've worked through and again after fixing those it popped back up. It had a terrible death rattle from missfires when gas engine kicked on but that was fixed by new spark plugs. I also cleaned the intake and egr pipe and replaced the PCV valve while I had it all out. After that the car ran great. I did an oil change and let my wife drive it. A day later it was making a bunch of noise again. I feared the worst that the pressure plate springs in the transmission were giving out. I checked the tranny fluid and it was very dark. I got new fluid and changed it and it has been shifting and running very smoothly. Except for one slight rattle when accelerating. Particularly up hills going slow when the power mode kicks in. I think it's too noisy on road with traffic to hear when driving up big hills fast.

When going up steep hills from slow and giving it gas as it hits power mode there's this rattle sound, hard to tell where it's coming from. It sounds like engine/transaxle zone. I've checked under the exhaust and everything is in tact. There's a possibility that the heat shield is rattling but I'm not convinced. I've been trying to record but It's not super consistent and so I don't have a good recording yet.

Now that the P0401 EGR insufficient flow came on again I'm starting to think it's connected. I haven't pulled the whole EGR and cooler to clean yet for two reasons. I wanted to check the magnet motor on the top. An easy check. Which I did today and discovered some small pieces of plastic, or magnet more likely, inside. It was definitely inhibiting the magnet from rotating up and down smoothly. A close look inside the magnet shows that the stop slide/little wedge at the top looks to be breaking down from all the spinning and stopping.

I cleaned it out as best I could with compressed air and blasted off the spring shaft and lower bearing. Put it back together hoping for the best. Reset the computer and sent my wife on her way for now. I think her driving to and from work 35mph top speed and little to no hills is what's keeping it from tripping the code. Because we haven't taken it on the highway since I reset it. I took it the other day for a test drive and that's when the code triggered again. High speed and big steep hills. So far it's stayed off.

I'm also holding off on pulling and cleaning the egr because I read about Toyota Service Bulletin
T-SB-0027-16 which says they extended coverage relating to an issue with the EGR valve and check engine light code P0401. So I'm going to call the dealer and see if they'll fix it for me, rather than me spend any more time tearing apart the system my self possibly breaking something or just throwing money at the problem.

I'm trying to determine if the rattle sound I'm hearing is related. Maybe it's the egr valve not opening properly and rattling around due to the magnet failing or a clog etc.

Just trying to see if people have had the dealer fix this issue?

I also have the peeling paint issue which is a total bummer and has just started getting really bad recently. I know some people have gotten a TSB about it, I'm just trying to figure out how to get that dealt with.

Mahalo nui loa for your input!

Max

 

Thank you guys for your info I appreciate the time.

I'm about 95% sure it's not head gasket, three reasons, oil was clean, no gummy cap or mess, not losing coolant, and did a block test with liquid and showed normal. I did all that before changing plugs, after cleaning intake and changing pcv, because I hate throwing money away. Thankful that the new plugs fixed the missfires. I was going to do a compression test but I don't have the tech to do it. It's running perfect otherwise since changing plugs, oil change, and transmission fluid change. I do wish I had known there was a trans filter that could be changed because it would have been nice to see if there's any pieces of springs or plastic holders from pressure plate in there. I suppose it's not too late and can just reuse the fluid I just put in.

Since I'm getting the code for egr and the magnet seems damaged I'm leaning to it being an EGR issue. Although I'm not ruling out a trans issue at this point.

Still hoping Toyota will replace the egr, something tells me that they aren't gonna spend the time to clean the system when they can just bolt a new one on in a tenth of the time.