MPG plummeted after ECU reprogram

[queenbetty]

A month ago the "Hybrid System Failure" light came on ('07 TCH) for a few minutes, upon restart was off. Dealer repair invoice states:

"Internal PCM Failoure TSB # 0102-09 .80 Code EG-5045 Reprogrammed PCM and Hybrid Unite rPer TSB for Code POA84"

Prior to the reprogram of the PCM (I assume that's what I'd call the ECU) I consistently got 32-33 mpg city with AC on, and 38-39 mpg highway. Since, city is about 29, highway about 32, per the car's calculation. Car also seems to "bump" at various low speeds, almost as if engine is turning on and off, but there's no indication it's doing so...in other words, the smooth drive-train transitions seem rougher.

In searching for similar information I came across a post elsewhere which says the following:

"If you're a Toyota/Lexus hybrid owner who had their car (not hybrid) battery die or get disconnected for service and have seen your MPG drop off along with a change in vehicle performance, there is a fix for this issue - you must reprogram the car's ISC. This can also help you if you noticed a sudden drop in MPG and a change in vehicle behavior even if the battery was not disconnected.

You can take the car to the dealer for this service, or you can follow these instructions and do it yourself...

1. Drive the car for at least 15 minutes under engine load to warm the engine and coolant to normal operating temperature

2. Park the car, shift into P, turn off all electrical (air conditioning, radio, lights, etc.)

3. Turn the car off, then back on

4. Set your hybrid status screen to show the battery charge level

5. Hold the brake pedal down, shift to D, continue to hold the brake pedal down all the way, then press the gas pedal down until the engine comes on and begins charging the hybrid battery. The car will not move or attempt to move, so don't worry - but the brake pedal must be kept firmly down

6. Repeat the above for 30-40 second intervals until the hybrid battery is fully charged - the battery status will be green and full and you'll notice the engine stops revving when you press the gas pedal down

7. Shift back into P, turn the car off for 5 seconds, then back on and press the gas pedal enough to kick the engine on

8. Let the engine continue to run on its own (no pedals) until it cycles and then shuts itself off

9. Either drive off at this point (you can turn AC, radio, etc back on), or shut down

Your ISC is now reset and your mileage and car behavior should return to normal. You'll need to do this anytime your car battery is disconnected for service or goes dead for some reason....or you notice the car is spending more time with the engine on and your mileage drops. "

1. The above seems like a practical joke; is it for real?

2. Should I go back to the dealer (fate almost worse than death)?

3. Is there something I can do to fix this problem? I have not changed my driving habits or techniques, all the mpg figures include AC operation, similar ambient temperatures.

BIG TIA

[honest_abe]

Originally Posted by queenbetty

A month ago the "Hybrid System Failure" light came on ('07 TCH) for a few minutes, upon restart was off. Dealer repair invoice states:

"Internal PCM Failoure TSB # 0102-09 .80 Code EG-5045 Reprogrammed PCM and Hybrid Unite rPer TSB for Code POA84"

Prior to the reprogram of the PCM (I assume that's what I'd call the ECU) I consistently got 32-33 mpg city with AC on, and 38-39 mpg highway. Since, city is about 29, highway about 32, per the car's calculation. Car also seems to "bump" at various low speeds, almost as if engine is turning on and off, but there's no indication it's doing so...in other words, the smooth drive-train transitions seem rougher.

In searching for similar information I came across a post elsewhere which says the following:

"If you're a Toyota/Lexus hybrid owner who had their car (not hybrid) battery die or get disconnected for service and have seen your MPG drop off along with a change in vehicle performance, there is a fix for this issue - you must reprogram the car's ISC. This can also help you if you noticed a sudden drop in MPG and a change in vehicle behavior even if the battery was not disconnected.

You can take the car to the dealer for this service, or you can follow these instructions and do it yourself... [I]

[Description of procedure removed to save space]

1. The above seems like a practical joke; is it for real?

2. Should I go back to the dealer (fate almost worse than death)?

3. Is there something I can do to fix this problem? I have not changed my driving habits or techniques, all the mpg figures include AC operation, similar ambient temperatures.

BIG TIA

It can't hurt to try it. I used to have a Ford Taurus and reprogramming the door locks to not lock when the car moved forward was almost as silly. It worked.

If it fails to fix it, then take the car back to the stealer.

[LittoDevil]

I've never posted here before but have always been reading.. but this post has me wanting to give you just my experience with the TCH.. I have the 2007 and it has about 70,000 miles on it... my real life mileage has been more like the one you stated after your car got serviced... I typically don't get about 38-39 mpg on the freeway.. it's always been hovering around 32-33 mpg, maybe 34 if i'm always on the freeway but my mixed 2/3 freeway and 1/3 city has been around 32-33 mpg.. so.. not sure if that helps but.. just thought I chime in

Larry

[honest_abe]

Originally Posted by LittoDevil

I've never posted here before but have always been reading.. but this post has me wanting to give you just my experience with the TCH.. I have the 2007 and it has about 70,000 miles on it... my real life mileage has been more like the one you stated after your car got serviced... I typically don't get about 38-39 mpg on the freeway.. it's always been hovering around 32-33 mpg, maybe 34 if i'm always on the freeway but my mixed 2/3 freeway and 1/3 city has been around 32-33 mpg.. so.. not sure if that helps but.. just thought I chime in
Larry

Ugh! How fast do you drive? Is it uphill both ways?

On 45MPH roads with few lights (for distances of at least 10 miles) driving at 50MPH, I get about 42.

In town with 35MPH limits doing 35-40 and plenty of stop signs and lights, I get in upper 30s.

Freeway driving 65-70MPH I get about 40.

This is w/o air conditioning on.

I am not a hypermiler so I accelerate normally.

[pinchepunx]

Did you resolve this? I am getting my 2008 next week and would like to watch out for this. Thanks!

[ukrkoz]

well, here's info from place else:

Thanks for pointing out the existence of TSB EG026-05. If you find that the engine runs too long when the HiHy is traveling at low speeds or at a standstill, then its reasonable to think this TSB applies to your vehicle.

After reading the TSB, it appears that you may be able to DIY without access to the Toyota diagnostic laptop. Make sure the engine is fully warmed up by driving on the freeway for an extended period - say 10 miles; or else by sitting in place and revving up the engine while the gear selector is in P, until the radiator fan comes on.

Then fully depress the brake pedal with your left foot to hold the vehicle stationary, and depress the accelerator pedal 60-70% while the gear selector is in D, for 30 seconds.

Then shift to P, make the car IG-OFF, and wait 5 seconds. Make the car READY again, check that the A/C is off, lightly depress the accelerator pedal and release when the engine starts. Then see if there's any improvement in the engine turning off when you are coasting at low speeds.

this is for Highlander Hy, of course. also, procedure is done with Toyota testing kit hooked up.

did anyone here do this procedure and what is the result?

[oldmanfu]

Wow, my 2009 has a recent drop in mpg. i went to a cold winter in MN and drop from 39 mpg to 32mpg. I used the bullentine above but it doesn't seem to work. The 2009 has no green light in the battery mode screen(just a battery sign with +,-). I remember prior to this issue, the computer shows dte at 500-530 mile range and now it indicates only 400 to empty. Any body knows if the bullentine above works for all hybrid year for 2007-20??.

[ukrkoz]

everyone has a drop in cold weather. it's a "florida car" if you want it to stay in good mileage range. also, it is "great planes car", as mpg is no good in uneven terraine states.
so, just chill and wait for warm weather and summer gas to return.
mine dropped from 42.5 to 36-37 winter time.
what's bullentine?

[oldmanfu]

i understand the cold weather issue. My point is that i got the same mpg as you do 34-37 in previous 2yrs, but now only 24-29mpg. When i stop and have no electrical items on, my conventional motor is on instead shutdown mode and sit on standby.

[ukrkoz]

well, let me put it this way. i had this question filtered through a different forum. EVERYONE agreed that mpg does go down winter time, because ICE stays on longer to keep HSD warm, for whatever reasons this needs to be done.
so, when you give such a big range, it averages to almost 36 mpg, which on a slight high end range for TCH, after revision for its mpg was done. now they say it's 32-36, with 34 median. 32/39 still makes it almost 36 median.
the only way to have true mpg averaged is to reset your mpg ratings once, and do not touch it ever again. this gives true mpg average through years.
my first guess would be, if it DOES look suspicious to you still, which it shouldn't, is to check with your regular gas station, if they switched to gasohol. next, i'd say to change ur air filter to K&N one. when i bought mine, guy told me she averaged 36. she went up into 40s 3 weeks after that filter installation.
also, run few cans of Seafoam through the system.
but realistically speaking - there's not that much reason to worry.

oh, and btw, check tire pressure. mine went down to 23 on all four by themselves, and should be 32. that will reduce mpg sure enough.

[goden]

I had a recent experience during the winter where I was following a salt truck during snow storm. I tried to go around the salt truck because he wa slinging salt on my car when all of a sudden I heard the salt hit the bottom of the car and all the lights lit up on my dash. The hybrid battery status started rapidly dropping and a light came on that said something to the effect of hybrid faulure. I immediately stopped the car and it died.I sat there a minute because I was freaked out. When I pushed the start button the car came back on and seemed to drive normally and charged right back up. Every since then my milage has dropped off. I saw this article and tried it a couple of times but I am confused about 1 part. In step number 6 you said repeat the above for 30-40 second intervals. Which part are you talking about? Do you go back to the part where you turn off the car or just keep pressing accelator?

[danealle]

Let me just say that the procedure described in this thread does NOT have to be performed every time the battery is disconnected. I have disconnected my battery several times to do upgrades such as new LED taillights and other things.

Disconnecting the battery has NEVER caused a drop in MPG for me.

[ukrkoz]

this is what you do:

Hold the brake pedal down, shift to D, continue to hold the brake pedal down all the way, then press the gas pedal down until the engine comes on and begins charging the hybrid battery. The car will not move or attempt to move, so don't worry - but the brake pedal must be kept firmly down


Repeat the above for 30-40 second intervals until the hybrid battery is fully charged - the battery status will be green and full and you'll notice the engine stops revving when you press the gas pedal down

[assailantsky]

Thanks queenbetty and ukrkoz for pointing out the TSB and the relearning procedure. I reckon my problem described on my previous thread is related to this. I just did the procedure today and I'll let you know how I go with this...