'15 Prius C Experiencing 'Prius Death Rattle'

So, my coworker's '15 Prius C is experiencing the 'Prius Death Rattle...' Vehicle has 120K on the odometer and my coworker drives 45 mins (30 miles each way) into work and home. So mileage is primarily highway, not sure if she uses Top Tier fuel only.

There is no milkshake in the crankcase and her coolant overflow tank is near full (This doesn't eliminate an HG failure. To my knowledge, no one has done a compression, leak down test, and/or test for exhaust gas in coolant system.)

So when does it occur? Rattle / shaking every once in a while during cold start-up (resolves in 5 to 10 sec) and there is rattling and loss of power under low load when vehicle is at operating temperature (think stop and go traffic).

There are no codes being thrown and I am assuming there are no stored or pending codes since everyone relies on the OBD2 port for diagnosis.

Dealership 1: Replaced spark plugs (couldn't reproduce issue and sent her on her way)
Dealership 2: Rearranged ignition coils (couldn't reproduce issue and sent her on her way)
Independent Garage 1: Can't reproduce the issue and at this point is pretty much saying that since they can't reproduce the issue and since there are no codes, they don't know what's wrong (suggesting that she picks the vehicle)

At this point, I am pretty certain that it is the EGR circuit since these symptoms are pretty similar to what happens to the Gen III when this is clogged, but no one is willing to look into this at this point because you know this would require some investigative work. The second independent shop (Yota specialists) that I called talked to me for a bit about it and the guy said it was 'interesting' and if there is no codes that he probably wouldn't be able to diagnose it unless he was able to reproduce the problem when he had a scan tool plugged in.

Does anyone know if the EGR valve is a solenoid that operates when either a voltage is applied or removed? Does Toyota have a checklist on how to troubleshoot a potentially malfunctioning EGR valve on the Prius C in the Toyota Service Manual?
Does anyone know of any TSB's for this issue on the Prius C?

Thanks!

I don't have time like I used to since I have a lot on my plate nowadays even though my gut is telling me EGR circuit, but it seems like no one is actually willing to diagnose this properly. So I may take it upon myself to look into it.

 

Our '10 Gen III had the death rattle a hand full of times and the EGR was clogged solid when I took it apart. It only threw a P0401 code once (Jan 2020 @ 151k) and it started to rattle under low load around 110k to 120k a few years earlier, but never did the rattle at start until it was below freezing when we drove to Ohio for Xmas and the car had sat for a few days (maybe 2017 or 2018, probably around 130k). The symptoms described above are exactly what I noted in our vehicle (would note shaking, rattling, and loss of power in traffic and symptom would dissipate if you hit the gas harder [i.e. increase air flow and reduce vacuum]). I always thought it was driven by oil mist being recirculated into the combustion chamber as the car burns oil (piston ring issue), but the car still burns around 0.25 qts/1000 miles. The other thing is that I have an oil catch can (OCC) installed on our Gen III and replaced the PCV valve around this time, but I am pretty sure the main culprit was the EGR circuit.

I cleaned and replaced every part in the entire system and have not had any issues since. The HG was not the source of the cold start rattle.

It may be a combination of reduced exhaust gas flow, dirty/fouled MAP/IAT, oil mist recirculation, and potentially slightly dirty injectors, but this can definitely happen prior to HG failure.

What I want to do is figure out how the ECU talks to the EGR in closed loop (when the car is first started) or under low load, because it seems that the metering of exhaust gases by the EGR valve 100% can cause this rattling to occur.

*EDIT* Maybe I should look at the LTFT and STFT and clean the throttle body and MAP/IAT for good measure when I inspect the EGR circuit.

 

Thanks! Appreciate it!

 

Interesting. Based on the other thread, this misfire in theory could be caused by a sticking EGR valve that is remaining open and not closing fully. You can comment on this, but the EGR valve opening alters MAP readings and results in a lower amount of vacuum and the ECU responds by altering throttle position and fuel delivery?

This is weird though because the ECU shouldn't be referencing all the sensors until it goes into closed loop (this typically takes 30 sec to a min on most cars - maybe the upstream O2S is heated up before the ICE turns on and the ECU is always in closed loop?), but it may be that the EGR system remaining open could be acting like a vacuum leak?

This is actually going to require legitimate diagnosis and probably me reading through the Toyota Service Manual or finding a shop that will actually work with my coworker to figure out what is wrong and not just send her on her way when there is no CEL.

Seems like checking voltages across TPS, MAP/IAT, and EGR valve and removing the EGR tube to checking for carbon fouling are all legitimate things to look at.

I think the coils should also be checked as well, but it sounds like there hasn't been a misfire code.

Best source for Techstream?

 

Coworker dropped it off at my mechanic who agreed to look at it and actually diagnose it.

Looked over it for about 30 mins and he also thinks it's a sticking EGR / clogged EGR circuit.

Will report back when she gets it back.

 

Ohh it is 100% nearly identical to the Gen III design (it is fed post-cat) and the circuit is fed a bit differently and easier to access. I tried to explain this to the first independent shop she took it to and the second shop I called and talked to on the phone. Mechanic I spoke to basically didn't believe me because there are "5 codes associated with the EGR system." I replied that it won't throw any of these codes unless it fails within the parameters that Toyota has defined. He replied, "Yeah, that's right."

No one was willing to actually diagnose the vehicle because it wasn't throwing a code for one main reason - $$$$$. Why are they going to take an hour or so to maybe or maybe not correctly diagnose an intermittent issue with a vehicle when they can do a brake job and 2 oil changes in the same time?

ASE certified mechanics my A$$. It's kind of sad. No one cares anymore.

 

As have I. My family owns a machine shop and auto parts store.

It's called customer service and having someone's vehicle for a week because you don't have a technician that has the time or experience to troubleshoot the problem is ridiculous. There are TSB's available and if you actually paid attention during your ASE classes, you should know how the ECU talks to the sensors. There is also ALLDATA and databases that describe common problems associated with vehicles that are encountered and the solutions.

Three of the shops held the vehicle for a week each. That is absolutely absurd.

You seem to have an issue with reading comprehension. The rattle doesn't only happen at start-up. It occurs under low load and also when the vehicle transitions between between electric and the ICE turning on and yes, it happens intermittently, but if you are a seasoned mechanic, you should go down a check list of what it could possibly be and eliminate each one step by step.

Like I said, this is about money, but if you are running a profitable business, possible losses like this should be baked into your cost model.

 

My coworker heard back from the mechanic, the EGR cooler was clogged through solid. He attempted to clean it and is just going to go ahead and replace it. He also ran diagnostics on all the other sensors and everything is within spec - TPS, MAP, coils, etc.

Not sure if this is the first report of this occurring on an EGR cooler that is fed post-cat; however, this is a bit concerning in terms of the impact and possible maintenance costs for all of the engines in the current Toyota line-up that run an EGR circuit.

What is the best way to extend this timeframe or prevent this from happening? I know that Toyota states to use their injector cleaner (PEA based) every 5k in their engines on the maintenance schedule.

Maybe this will reduce the amount of carbon that builds up?

 

Looks like it from the diagram.

Screen Shot 2021-05-20 At 2.48.44 PM by jburg posted May 20, 2021 at 2:51 PM

 

Just wanted to update everyone, the EGR cooler was replaced and the EGR valve cleaned and the car is running as good as new.

The EGR circuit CAN clog on the post-cat fed systems. Just going to wait and see what happens on the M20A-FKS and A25A-FKS engines in the coming years, my gut tells me the system is either going to be eliminated, exhaust gas routed from the second cat, and/or they are going to introduce a system that cleans the EGR cooler.