MPG Issue

I would approach the problem by repeating benchmark runs and comparing them to my baseline:

1. Under 40 mph - to identify problems with the hybrid control laws
2. 55 mph or faster - to identify problems with engine and drive train

The benchmark uses cruise control over two, opposite runs over the same 10 mile route. The two runs average out wind and elevation effects. The cruise control minimizes operator variability. It needs to be a route free from traffic lights and stops. Once the car reaches the target speed on cruise control, clear the trip meter. At the end, record the distance, MPG, and average speed, cell phone camera works great. Then we compare your results with mine:


You mentioned an "OBD" scanner that turned off the continuous backup beeper. What is it? Does it have a data recording capability? We can use it to compare some of your vehicle operations with ours.

Bob Wilson

 

You might have a trailer Prius described in this thread Possible undiscovered performance and MPG issues with Prius v (lowercase v) | PriusChat

 

i hear you on the dealer, i hate going too. no, they won't take you seriously. you will have to force them to go for a ride with you, show them the mpg's and then take a ride in a new one. even down to the high 30's, they usually say it's within spec, but 30 should get their attention.

 

I notice on your carfax that one of the last things done to it was the EOE reflash.

This is the recall that Toyota instigated to change how the software works to protect the Intelligent Power Module.
I've had it done.
The vast majority of Prius Owners have had it done and noticed no discernible change in vehicle performance.
HOWEVER....
There are a few stories of people who claim to have had the EOE reflash and then suffered plummets in MPG. Usually resulting in Toyota having to replace the whole module.

Whether this is the problem or not? At this point I'd probably just let the dealership deal with it. Something IS wrong.

 

I thought the last advocate finally gave up when Toyota told him to 'pound sand.' I had not heard of the flashed ECU being replaced . . . as the replacement would have the same software. Now if there were a hardware difference, it might make sense.

Bob Wilson

 

I suspect I'm shooting at wind in the bushes here.
But there were a few posts where people had to have their entire ECU replaced after the software flash, and a few posts where people reported a reduction in gas mileage after the reflash. As far as replacement goes, the general feeling was that these were Prius where the recall came too late, and the flash only revealed the problem as it already existed.

Toyota did mysteriously extended our IPM warranty, AFTER the EOE recall.

Software doesn't always load correctly. There also early on were some reports of dealerships messing up the process. Evidently it was a two step process and some dealerships just weren't doing it right.

I wouldn't place any retirement funds on a bet that this is the OP's problem. But since it does appear that one of the last maintenance acts that was performed on the vehicle WAS the EOE recall, I might mention it.

 

If HV battery recharging is having a problem - check the battery inverter coolant level is good and the battery air intake cooling vents in the rear seat are clear. If you are doing 95% urban driving then use the power mode to rely more on the ICE and less on the electric motors and HV battery. check the tires for uneven wear - if the tire tread wear unevenly then get a wheel alignment. If hydraulic braking dominates instead of regen braking - have the hybrid system checked for problems.

 

I had something strange happen today:

• 9 AM (82F)- normal morning commute, due to high humidity, used AC at 78 to dry the cabin
• 11 AM (90F) - errand to meet wife at medical mall, no AC, to warm-up from office AC
• 12 PM (91F) - head to Red Lobster for lunch with wife and her companion, no AC
• 1 PM (92F) - back to work for meetings, AC @78, turned off before parking car
• 4 PM (93F) - headed to home, car parked in tree shade
  • "EV" refuses to come on, even with AC off and windows down
  • Windows down, car never auto-off the engine even descending modest hills, fully warmed up
  • At bank drive-through, facing sun, finally turn on AC @78
  • Reach home street, 1st auto-stop of engine
  • Parked, engine auto-stop for first time

Humidity is the one thing I can't handle, sweat doesn't cool effectively. So usually AC @78 is enough to dry out the car and make it tolerable. By noon, the heat is up but humidity down and I'll often drive with just windows. On the afternoon commute, I'll come out chilled by the office AC and as long as not in direct sunlight, drive home using windows down. But today was different.

My working hypothesis is the air inlet temperature to the traction battery was above a threshold that inhibited EV and engine auto-stop. But once the cabin was cool enough, upper 80s?, the car allowed the hybrid laws to work. Testing this hypothesis will be a challenge.

Bob Wilson

 

Well since I've been taking long shot's in the dark. I'm going to blame the whole thing on your lunch at Red Lobster.