Parasitic battery drain?

Can you be more specific?

Gen 4 Prius EGR is a radically departure from Gen 3, takes it's exhaust downstream of the catalytic converter, more-or-less doubles the cross-sectional area of components, likely a further redesigned valve and revised programming. According to pruschatter @jerrymildred (who worked for them),Tampa Hybrids had the opportunity to clean one such system with over 300k miles, barely any carbon.

We were the beta testers.

 

A gen3 will burn no observable oil in 5k with good rings and valve seals. A Corolla 1.8L engine with egr from the same era does not blow head gaskets routinely and no one cleans those egrs. What is different? Thermal cycling from stop start technology. Extensive changes fixed gen4 hybrids.

 

I know diddly about toyota's EGR fleet. I'm just asking questions. I now know what a '24 Corolla looks like externally.

Is Jerry saying a Gen4 can go 300k miles and not have the head gasket fail? And the EGR system wasn't clogged all ta'hayl?
Gen2's have a good record also, true?

 

This is a valid theory.
But then what about Prii such as mine where the duty is mostly hours on end at highway speeds?
But alas, I come into a city and the hybrid starts doing its hybrid thing.....

But then what about intake manifolds that have obviously clogged EGR ports on only one or two cylinders?

I can't wait to see what my intake looks like at teardown!

 

An important bit about the EGR introduced on the gen3 Prius was that it was a cooled EGR. The exhaust went through a heat exchanger to 'chill' it for improved emissions and efficiency. It took exhaust from about where traditional EGR systems do. That hot gas can have material dissolved in it. Not a problem for tradition systems, but the cooling causes any material to drop out to form clogs.

Taking the exhaust from past the cat in the gen4 means it has cooled some beforehand. Some potential deposit material will have dropped out before getting into the EGR. More importantly, the hydrocarbon emissions that are the likely deposit source are reduced by the cat to CO2 and water.

 

Exactly. Well, unless their Exhaust Heat Recovery (EHR lol) springs a coolant leak, and goes on long enough the coolant runs out, then head gaskets can blow.

Gen 2's are pre-EGR, at least full-blown gen 3 style. I'm not that conversant with them.

BTW, I like what you mentioned, about your loaner having EGR feed in the middle of the intake manifold, presumably for symmetrical branches.

 

Traditional EGR systems date back to the early days of emission controls. They let exhaust gas replace air to keep the stoichiometric rate correct under light engine loads to reduce emissions.

 

@Tideland Prius, perhaps remove all posts regarding coolant/EGR/head gasket and move them into a new maintenance thread?

 

Good point, but too arduous? Topic derailment is a way of life here.

 

" This could still be a software bug improperly enabling things that shouldn't be during charge also. " That's exactly what the problem is, and Toyota will fix it under warranty if you insist on it. They claim they updated the firmware (or software) on my 2023 Prime and I'm hoping the problem is resolved, but since it was intermittent, it's too early to say. All of the nonsense I'm reading online about the charging session causing the problem is completely foolish. Even Toyota service techs told me that's complete bullshit.

 

Toyota did release a TSB for some 2023-2024 vehicles. TSB 0054-24
12V Auxiliary Battery Charge May Deplete When PHEV Charging Cable has an Extended Connection Without Charging

Back in August, I experienced a dead 12 volt aux battery. I thought the TSB might address my issue. I printed a copy of the TSB along with my experience on the car to the dealer. Deer in the headlights look.....they knew nothing about this TSB. The fault isolation they did on my car was basically charge and test battery, made several starts OK. I have more than 50 years experience troubleshooting complex aircraft systems and working on cars since I was 16. My opinion of Toyota techs.....I'll leave it at that

Last fall, I tested my car for parasitic or dark current as Toyota calls it. Toyota limit for dark current on the Prius is 120ma per their procedure. I installed an ammeter in series with the negative terminal per Toyota procedure and measure a slow fluctuation dark current between 20 and 50ma. So I averaged it out at about 40ma. I have a battery monitor installed and left the charge cable installed for about 16 hours on 2 occasions. No significant drop in the aux battery voltage from the graph the BM records. This confirmed my car was not subject to the TSB.

Installed an AGM battery back in October. Been working excellent since my longest trip is @25 minutes with most shorter in the 10-15 minute range.

Cheers

 

I think the second half of the thread at the moment, like 100 posts. LOL

 

That is very interesting information. Thank you for sharing it. It directly contradicts what the dealer tech told me. If I’m to believe what my service record shows, the problem I’m experiencing has a different origin. No service bulletin was referenced in my service record. It refers to a parasitic draw DCM, which was reset. I can only hope the problem is resolved.