Lawsuit: Prius recall for inverter software fix hurts fuel economy

[MetroMPG]

An electrical engineer who routinely tracks the calculated MPG of his 2013 Prius noticed a significant drop in efficiency following a recall (software change) meant to fix a problem with overheating inverters in the cars.

Toyota recalled 800,000 cars in the U.S. to apply a fix that may have reduced stress on the hybrid components by increasing the share of work done by the gasoline engine. When asked directly, the company hasn't denied this may have affected efficiency.

A class-action suit is in the works:

Assertions that the Toyota software change decreased the car's fuel economy are contained in a lawsuit seeking class-action status filed this month in U.S. District Court in Los Angeles. "Unbeknownst to drivers, Toyota reduced the vehicles' fuel efficiency, which is the main reason why consumers purchase Priuses," it alleges.

To add insult to injury, Toyota is also being sued by one of its dealers, which alleges the software update didn't actually fix the problem; it only delays the failure.

Cherry on top: "a complaint by the dealer is now under review by the National Highway Traffic Safety Administration" because the problem can cause the car to suddenly enter "limp mode" (drastically reduced power output) without warning, including at freeway speeds.

Source: Toyota Prius software fix may reduce fuel efficiency, experts say

[Daschicken]

All things considered(lawsuit), wouldn't it be cheaper to just put in a bigger radiator for the inverter?

[MetroMPG]

I dunno.

The article says the problem is solder joints on the IGBT's that crack due to heat stress/thermal cycling.

Are they bathed in coolant? Or on a heat sink that's bathed in coolant?

[UFO]

Sounds like they may have undersized the IGBTs and failed to deal with conducting the heat away. Solder joints are not typical places to dissipate power, so it must be the devices themselves that are dissipating too much power.

[redpoint5]

Hmm, my 2012 plug-in must use a different inverter since I was never notified about a recall.

I just have the usual Takata recall to complete as well as something about a high power fuse needing to be replaced.

[gone-ot]

We haven't (yet) heard anything from Toyota about this recall for our 2014 Prius.

[S Keith]

Originally Posted by Old Tele man

We haven't (yet) heard anything from Toyota about this recall for our 2014 Prius.

It's possible you had a late model 2014 that was produced after the recall and are thus excluded by VIN. You can go to http://www.toyota.com/owners, create a profile, and add your vehicle. It will notify you of any safety recalls.

[Vman455]

Originally Posted by redpoint5

Hmm, my 2012 plug-in must use a different inverter since I was never notified about a recall.

I just have the usual Takata recall to complete as well as something about a high power fuse needing to be replaced.

The inverter software recall was announced in early 2013 (I had mine done in April 2014), so it might have been done by the previous owner.

According to Toyota's most recent update, no Prius models are involved in the Takata recall.

[Vman455]

Originally Posted by MetroMPG

An electrical engineer who routinely tracks the calculated MPG of his 2013 Prius noticed a significant drop in efficiency following a recall (software change) meant to fix a problem with overheating inverters in the cars.

An apparent drop of 5mpg may be related to any number of things. What was the weather like? Traffic? Did his commute change? Did he start going to a closer grocery store that didn't allow the engine to warm up fully? Did his car develop an undiagnosed dragging brake caliper? Does his car have a clogged EGR? Has his PCV valve stuck? Does he use AC or heat more now than he used to? Any of these things could explain a change in fuel economy as drastic as he claims. Then there's the issue of the claim itself: 49 to 44 over how many tanks? How consistently? How meticulous are his records? Is this claim accurate or an estimate?

As an illustration of a possible counterargument, after I had the recall performed in early April 2014, I had a run of 9 tanks in a row at 60+ mpg, then one 59 mpg, then 6 more 60+, through October of that year. Using Enger's reasoning, the recall improved my car's fuel economy drastically! Except it didn't, because we haven't controlled any variables except the software update, so we have no way of knowing what effect it has on fuel economy by itself.

The Prius has an EPA fuel economy rating of 51 miles per gallon in city driving for the 2010 model and 49 mpg for the 2014 model. Enger said his city driving mileage dropped from 49 mpg before the software change to 44 mpg afterward.

This is a deliberately misleading statement: the 2014 is rated 49 mpg city because the EPA approved a new correction factor last year applying to 2011-2016 vehicles, leaving the 2010 with the original rating.

I don't know who's right here, but Enger has a lot to prove before I believe his claims.

[MetroMPG]

Given he's an EE who apparently tracks every tank (manually), I'd be inclined to give him the benefit of the doubt that he's comparing apples to apples. I'd be surprised if he made his complaint based on a single data point vs a long-term pattern.

But you know what happens when I assume ...

So those are all valid questions.