Latest Software Update Safety Recall Resulting in 8mpg less...

I found in town driving mpg's over 50 mpg but the highway driving over 65 mph where it would run way low mpg's Wish you luck but they wont be flashing it back to stock

Mike

wanderin around on my phone

 

Hopefully someday someone will "jail break" one or sell aftermarket EPROMs.

 

I have spoken with a few shops that considered trying to read/write to the car but it would take some money for the chassis dyno time. Lots of trial and error work to figure out what does what. If there was more demand for software changes then I could see someone taking the time and money to figure it out. The weak inverter would have to be addressed at a hardware level before pushing it via software mods. Certainly it could be modified to handle larger amounts of current.

I am just leaving mine bone stock. I don't drive it much since I bought a Kia Soul for a daily driver My Soul gets an easy 30 mpg and has a wicked audio system.

Mike

 

Well, I took 2 trips in the last 2 days and I guess the computer has been trying to re-think itself since the recall was done. It is now back to its old self with a slight increase in mileage. The dealer must have unhooked the battery to do the recall and that is why my mileage was so p*** poor at first. They should have told me about the re-thinking process but didn't. Anyway I am a happy camper again, the dealer is happy also. Thanks to everyone for their input.

 

To get consistent low 40's mpg out of a Prius has to involve some type of nasty gymnastics. I've driven our Prius in all kinds of situations, from horrible extended Megalopolis gridlock stop and go traffic to furious Interstate Summer travel in awful heat and monsoon like downpours completely loaded with enough gear for a month's worth of travel for 2 people. Even some really cold weather travel is included in our driving mix. The worst I've done in our poor Prius is 48 point something mpg for a whole tank full of fuel. Normal tank to tank has usually been 52-54 mpg with our 2011. Our previous 2005 Prius averaged 50-52 mpg with a hand full of 53 mpg averages. I even installed 16 inch wheels and non LRR 205/55 16 tires on that second gen Prius after the first 4,500 miles or so of the 145,000 miles we eventually put on it.

Maybe if you're a mason or brick layer and tow your supplies and equipment with your Prius to a work site every day? I can't see how a Prius could achieve such low mpg, otherwise. Running low pressure on heavy duty 10 ply truck tires? Driving uphill all the time with 5 each, 200 pound plus souls on board? Someone's stealing gas out of the tank each night? Leaving a drogue chute deployed all the time? Worried about leaks at the local nuclear power plant, so had the Prius body lined with lead? Forgetting to turn the Prius off when parking it for the night?

Baffled and all out of guesses. Check the tire pressure, check the intake air filter, go to a different gas station for a while, unload the contents, if you're carrying stuff in your car all the time. A Prius should be able to at least get 45 to 50 mpg, fairly easily. Go rent another Prius for a couple of days and see if the same mpgs result. Prius might be a lemon? Just doesn't seem right.

 

This effect, short-term mileage hit after 12V reset, has been seen since the first 2001-03 model Prius. There are metrics accumulated and stored in the ECU memory that have an effect on mileage. Doing a 12V disconnect wipes them out as well as any recorded, error codes.

My current speculation is the 'cold start' fuel trim that has to be relearned after a 12V disconnect or ECU power-on reset. The car is probably built with a factory, default, cold-start fuel trim table. So as the car goes through various operating cycles, these initial tables are probably adjusted for the car, gasoline quality, and its altitude. Also, in engineering we often have to know the calibration offset of our instruments to get accurate readings. So I'm speculating that the initial drive cycles are in effect relearning the calibration constants for that particular car's MAF, injectors, and other engine sensors. The production line parts are going to have some variability that can be measured in operation to achieve efficient operation after starting the car.

Bob Wilson

 

Understand the reflash and battery disconnect/reset. What I don't understand are the comments from drivers who state that they can only achieve lower 40 mpg rates with their Prii on a normal basis, whether the car has been flashed or not.

 

Recently, I disconnected the battery, charged it overnight and reconnected it. I had about 4 gallons of gas in the car at that time and by the time the empty tank indicator came on, I was averaging 63-64 MPG. After getting a tankful of gas, I reset the Trip B like I always do and now the best I can do is about 57 MPG. Actually it was more like 53 or so MPG right after the reset of Trip B and it has slowly crept up to 57 MPG with much work. I wonder what a Trip B reset does. The only difference I can think of between connecting the battery and the later reset of Trip B is that when I reconnected the battery it was showing about 13.1V and later right before the time of the Trip B reset after refueling, it was reading about 12.4V (when the car was stopped while getting fuel). Very strange behavior. I am going to try to replicate this.

 

Your 12V battery sounds marginal. When you get a chance, open the back and measure the 12v battery voltage. With the car off and the hatch open, a value less than 11.8V means that battery is toast.

Bob Wilson

 

Hello Chris, at least your post tells us we are not crazy. We took our 2010 in for the computer update recall in March or April 2014. We had consistently been getting 50-52 mpg and made it all the way up to 58 on a long road trip. on the drive home from the dealer (after the update) out mileage dropped to 42 mpg on the highway. We watched it for a week or two and could not get above 45 tops but usually 40 which is a far cry from what we are used to. We took it back to the dealer and they did a reset and said that they couldn't find anything wrong. The second time in the shop has now dropped our mileage to 35 mpg-40 tops. If we can't get our mileage back, there is no reason to keep a Prius! We did check tire pressure, changed gas, etc, nothing has helped.

 

Where are you located (city/state)?

The reason I ask is there are a number of independent Prius shops who might be able to give a clue. We'll also work with you to help fault-isolate what is going on.

Bob Wilson

 

My wife n I had rented 2 Prius that had the update and both cars ran high 30's to low 40's mpg when driven normal. The one we rented in Minnesota is the one I reported on which I drove for a couple thousand miles. No way was that car learning anything for that many miles. Why some report good mpg's and a few report absolutely terrible mpg's is unknown to me anyhow...

Mike

wanderin around on my phone

 

On the equipment I work on this factory default is known as "initialization". Sometimes I have to force a default setting before I can begin troubleshooting. Many of the non vollital memory (NVM) location settings will drift out of range over time, depending on operator settings , but still function. A factory default setting gives you a known range to start from.

Back in the day cars weren't so smart. I put am exhaust system on Jimmy Buffets 64 Fairlane. I drove it from the shop back to his mothers house and he brought me back to the shop. He had 2 porches sitting in the driveway. I asked him why he had 2. He said one was set up to run at above 3500 ft above sea level. He bought that one when he was living in Colorado.

 

Carb jets . . . <ARRRGGGGHHHH!!!!>

Bob Wilson

 

Isn't it easier to pop the hood (getting in from passenger side ???) and use the terminals there then getting to the battery in the back ?? Even better if someone has a garage to pop the hood in the evening so no need to get into the car and measure 12V battery voltage on the terminal ??

 

I AM HAVING THE SAME ISSUE...IT IS NOT THE TIRE PRESSURE. MY GAS MILEAGE DROPPED FROM 48 TO 34.

 

My radio was okay.

 

I posted in another thread, but now that the weather is consistent, I'm down from the computer showing a regular 54 or so on my AM commute to 49-50. AM commute usually has minimal traffic, so it is a better test scenario. Overall tank-wise and trying to be comparable on temps, I averaged 47 last October and 44 last month. Even before the recall my FE dropped like a rock in the cold, so I was hesitant to blame the software initially when there were still hints of cold temps around. I do need to double check the air pressure.

You can see from my sig that I'm no hyper miler, and understand if I flog the thing, I won't get 50 mpg, but I used to at least get consistent numbers from that AM commute.

 

is all this due to the priuschat update?

 

Ha!!! Beer just came shooting out of my nose when I read that.