Transmission slip??? Dangerous problem I'm having

I'd be surprised if it was the transmission - it's not a conventional type of transmission, no clutches as such, but 2 Motor/Generators and an Internal Combustion Engine driving through an epicyclic gearset (called a Power Split Device). It sounds like one of the 3 power sources isn't doing what it's supposed to.

There is a thread on something like this - but I'm not sure if it's been resolved:
Loss of Power on Canyon Road!!! | Page 4 | PriusChat

 

I would take it to another dealer if you have lost faith in your dealer. When you have a warranty it does not matter which one you go to. I would agree the transaxle is not likely the problem but you probably have some issue with the engine or, less likely, the controls. Here's a deep dive into the transaxle that is one of a series of college level courses by Weber Auto. It can help to know more when you are talking to service advisors.

 

I see your location is Arizona.

Some questions :

• How hot is it out when this happens?
• Is your car parked in the sun?
• Do you use window tint or sun visors to ward off the heat intrusion into your Prius?
• Is anything blocking the intake vent to the hv battery fan?

If there are no codes and and the problem is intermittent, I’d look at the electrical portion of the equation .

Hot batteries can cause problems to be intermittent, particularly if demand is placed on them.

Good luck and keep us posted .

 

Welcome.

1./ From your descriptions, it sounds like an electronic control issue, not a mechanical issue. If the dealership cannot diagnose the issue, and you perceive it to be a safety issue, place a call to Toyota direct and see what results.

2./ There are numerous reputable 12V battery options in the $150 range.

 

Try turning off the traction control, see if that makes any difference.
Putting the car in drive whilst it's going backwards, at any speed, is not good practice so I would discount that as a fault.
But the lack of power when setting off could be the traction control kicking in for some reason, could be a loose or uneven surface, different grip on each front tyre due to wear etc.
If you turn off traction control and the car skids as you set off then it's either the road surface or the tyres, not the car, that's at fault.

 

The book specifically says not to do that - but I think there's a lock-out anyway. But, I'm sure we've all beaten it by a few milliseconds, and it hasn't objected.

REVERSE is EV only - it can't use the ICE in reverse. But then, the car always starts in D in EV, even if for just a nano-second or 10.

I'm wondering - you said they did a software update and it was fine for a month. I'm wondering what would happen if they did it again. Even though it should be loaded for good, we don't understand exactly what a "software update" does.

The reason I'm wondering that way, I've got an MP3 player which I use a lot of the time while I'm pottering around the house. And occasionally it's locked - their answer is to run a "firmware update" - I've done it twice in the last year or so, and interestingly the 2nd time when I downloaded the file to update with, it was the same file as before. I thought - hmmm, I've already done that, but no, it's worked fine again for 5 months since the 2nd update.

 

I would like to know more about the software update. What is involved. Has a Toyota technical service bulletin been issued?

My dealer wants close to $300 for a new OEM 12V battery. Nothing is cheap about this car.

 

You've hit the nail on the head...without warning lights and codes, nobody is going tear into it and start replacing components willy nilly, especially under warranty (Toyota's dime). And you wouldn't want them to do it on your dime either. The components you're talking about are not cheap.

Have you checked the voltage of your 12V? Have you tried disconnecting the 12V (negative terminal) for a few minutes and re-connecting? How's the coolant level on the electric side? You haven't said what the state of charge of the traction battery is during these incidents?

As has been said, there is nothing like a clutch in this drivetrain that can slip. If you're losing power, it's got to be a control issue. Either the throttle is not sending the right signal to the computer (have you tried the various drive modes affecting the throttle mapping: Eco, Normal, Power?) or the hybrid synergy drive is not responding the inputs from the computer.

Another "way out there" possibility is damaged wiring, rodents? Really grasping at straws here.

 

An extended warranty comes with completion of the IMG control firmware TSB, presumably because damage to components could have occurred prior to accomplishment of the TSB.

You can buy a comparable (arguably better) battery for $150 and DIY install.

 

That may be true of an update for older Prius cars. For a 2016 or 2017 Prius Two, I know of only two updates for the hybrid system, described in T-SB-0241-17, “Reduced Power When Accelerating From a Stop,” and T-SB-0014-18, “MIL "ON" DTC P1CB7A2.” Neither bulletin mentions a warranty extension, just that the repairs are covered under the hybrid vehicle system component warranty (8 years/100,000 miles).

When the car goes in for service again, I’d suggest making sure that the technician checks not only for Diagnostic Trouble Codes, which has probably been done already, but also for Vehicle Control History events, which I described in post #9 of a previous thread.

I’d also ask if the dealer has opened a case with Toyota’s Technical Assistance System (TAS), the dealer-only support line; this is one sign of a serious effort. If the dealer has offered to have a Toyota Field Technical Specialist take a look at the car, I’d encourage you to take them up on this, too.

That’s true (see this thread, among many tedious others), but I’m not sure I’d do it just yet, unless there is evidence that the battery is faulty, to avoid both needless expense and possibly complicating the situation by introducing an aftermarket component. (@Brenton Boyd may have mentioned the battery just as an example of an expensive part.) Every dealer should have a battery diagnostic system (see post #10); if they were to say the auxiliary (12-volt) battery is bad, they should be able to back this up with a printout from the system.

 

My dealer has never mentioned any of those TSBs when I come in for service. And I never received anything in the mail from Toyota. Only one thing has come in the mail... the Airbag recall notice.

What 12V battery can I get for a 2016 Prius? $150? Haven't been able to find one. Not even listed on the Optima site.

 

I am also curious.

Does this sound like your problem?

REDUCED POWER WHEN ACCELERATING FROM A STOP
TECHNICAL SERVICE BULLETIN
Reference Number(s): T-TCI-5019, Date of Issue: September 12, 2017
TOYOTA: 2016 - 2017 Prius
SERVICE CATEGORY: Engine/Hybrid System
SECTION: Hybrid/Battery Control System
MARKET: Canada

APPLICABILITY

APPLICABILITY

YEAR(S) MODEL(S) ADDITIONAL INFORMATION
2016 - 2017 Prius VDS(s): KBRFU
INTRODUCTION
Some 2016 - 2017 model year Prius vehicles equipped with a NiMH HV battery may exhibit one or both of the following conditions after repeated driving on long downhill slopes:

• When accelerating from a stop, or from extremely low speeds, the vehicle may have a reduction in power.
• The HV battery monitor on the multi-information display continually shows one bar, indicating that the battery State-of-Charge (SOC) is at its lowest level.

The Hybrid Control Computer (HV ECU) logic has been modified to reduce the possibility of these conditions. Follow the repair procedure below to address these conditions.

If you notice it is only for NiMH batteries.

 

It’s a service bulletin, not a campaign or recall; see post #9 in the thread about it.

I’m not sure what’s in stock at your Moon Base; the LRVs used primary batteries that aren’t likely to work. More seriously, try looking for non-AGM, “H4” or “LN1” batteries, like those discussed in several previous threads.

 

That's a great Prius commercial.

Mendel posted two links to Toyoya parts places that sell the OEM 12V for about $180. That's reasonable. Do they have to be charged first, or can I just toss it under the hood, and go....

I miss the days when I just drove up to Sears, and 90 bucks and 20 minutes later I was driving off with a new "Diehard" battery. (for Camry)

 

Unfortunately, I think this is simply, more and more the truth.

Don't get me wrong, the complexity of automobiles today, make it great that they can self diagnosis themselves with the ability to manifest codes that illuminate problems.
But I do think sometimes Service Departments and techs, are now limited by this crutch.

In 2010, I owned a new Honda Fit. I got hit from behind, very minor damage. It really wasn't a problem. But because the vehicle was so new, and there was some damage to the back bumper, I took it to the dealership and wanted them to inspect it.
I got the exact same reaction. The first thing they asked was, was it throwing any codes? When I said no, they defaulted to the idea that I had no problem then, and shouldn't worry.

What I wanted them to do was look for any visible damage they might be able to see. Any bent frame, or loosened bolt, possible suspension damage, etc....
But because the vehicle wasn't throwing a code? I had to BEG them to just take a look.

They eventually took the vehicle back and SUPPOSEDLY put in on the rack and looked, but to this day, I don't know if they weren't just humoring me.

The attitude that I couldn't possibly have a problem, because the vehicle wasn't throwing codes, was very frustrating to me. Especially because we were talking about possible structural damage NOT something engine related.

It may be similar for the OP. If it is something happening mechanically with the transmission but not something bad enough to yet trigger a code, then you get the "Wall" of there isn't a problem. Which I agree with the OP is unacceptable. You shouldn't be asked to, or put your self, family and others at danger because the vehicle isn't showing a code.
What? Drive it around until you DO get in wreck? Or it finally does manifest a code?

I don't have too much more to offer, other than I would start documenting every attempt to have it fixed and exactly what is done.
That type of problem can be dangerous and frustrating.

 

Maybe it's time to file a complaint with the NHTSA.


File a Vehicle Safety Complaint | Safercar.gov | NHTSA

 

Techstream is good for more than reading specific trouble codes the ECU decides to throw. Even if it hasn't thrown any, you can still look at live data, even record and graph it. For instance, you could record the torque and/or power being demanded of the engine and MGs moment to moment through a drive. It might provide more insight into what is happening. It also might provide a better case to be made to a dealer or service shop that there is something to dig into.

-Chap

 

If it's like my last 2 cars (FORD), it had a few software updates when it went in for service. One time, the car was driving appreciably differently (accelerator response) , and I mentioned it to service dept - they said that they plug it in when it comes in, and if there are any updates, they do them - not sure if automatically or they have to load it to the car? But the tech wasn't sure if there had been any for sure, it was his presumption.

 

I don't see why you can't do that. The gen 4 Prius uses a plain old regular 12v car battery with no hydrogen venting requirements under the hood. Anything that is the same size should work. Whether it would be the best option or not is a different story.