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Curious if anyone else has had this happen yet? We had 2000 miles on the new Sienna when it started saying “Hybrid System Failure, Contact Dealer”. We took it in and they said the main hybrid wiring harness has a faulty connector. The problem is, they don’t have a part to fix it. It’s been sitting in the maintenance bay at the dealer for over a month now with no ETA. They put us in a 2020 rental, but we are getting pretty irritated that we paid for a new van but we don’t have that new van. I actually think that after 30 days it qualifies under our state lemon law. Wondering if it’s a one-off issue or if this is going to be a systemic problem and Toyota ends up doing a recall for this wiring harness.
 

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I've had my 2021 Sienna XLE for about six months now and was getting great gas milage until about a month ago. It was getting 36+ MPG and slowly went to 30MPG then 27MPG and now at around 22MPG. My service center is informing me that they cannot find anything wrong with it. I use premium gas so it's not the gas, I just wonder if this faulty connector could be the issue as well.
 

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I've had my 2021 Sienna XLE for about six months now and was getting great gas milage until about a month ago. It was getting 36+ MPG and slowly went to 30MPG then 27MPG and now at around 22MPG. My service center is informing me that they cannot find anything wrong with it. I use premium gas so it's not the gas, I just wonder if this faulty connector could be the issue as well.
Is there a particular reason you are using premium, perhaps some local/regional reason?

Else, not doing anything benefit to Sienna but costing more to your wallet.
 

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I just started using the premium whe I noticed the drop in MPG. Thought that could be the problem.
Do a test run on a route with minimal stops and speeds around 55 mph.

Basically drive an ideal route and if still poor mileage [taking into account if using winter tires and winter gas penalty] then dealership needs to be furthered pressed.
 

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Costing me 14MPG to heat the cabin!? THAT doesn't even sound logical. It's supposed to be a Hybrid when they state 36MPG should all weather conditions have been evaluated before giving an average?
Well, it is a bit more than that simplification. Hybrid mileage is essentially based on the amount of ICE (internal combustion engine) off time the car has. The less ICE off time, the lower the mileage. The ICE is on longer to:
  • heat the cabin
  • ICE warmup cycle is longer
  • in the summer, the ICE does not generally come on until you hit 10 MPH; in colder weather (55 degrees F and lower), the ICE comes on shortly after starting the car. It then is on for the low speed maneuvering from parking to street, where in the summer it does not come on until you are on the street and under way.

Winter gas also has less energy content which means less MPG.

It also takes a bit more energy to move a cold car.

If you do just short trips (5 miles or less), there is a huge warmup component of those trips. Mileage depends a lot on what type of trips you make. I was consistently getting 40-42 MPG in local driving where the max speed was 50mph or so. Now I am down to 32 mpg for similar trips. Shorter trips make the mpg even worse.
 

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“Hybrid System Stopped - Steering Power Low”
I got this on my dash three weeks ago when I was going to pull out of my parking spot at the mall. I put the actual hand gear in reverse, the back up camera came on, but the car remained in park and that was the message displayed. After a couple more tries of putting it back to park and then reverse with no success, I turned the car off and back on, and the message went away. It has been okay so far…
 

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Costing me 14MPG to heat the cabin!? THAT doesn't even sound logical. It's supposed to be a Hybrid when they state 36MPG should all weather conditions have been evaluated before giving an average?
The MPG figures (whether by the EPA or the manufacturers) do include the weighted results of the "winter" driving cycle, but the testing methods certainly do not emulate all possible driving conditions.

Based on my personal experience, if the daily driving routine consists of a number of relatively short hops, separated by relatively long intervals (let's say 10 min vs. 90 min respectively), you'd be getting pretty lousy MPG's even in favorable weather conditions. This applies not only to hybrids, but also to ICE vehicles and EV's, only that in the EV's it's the cold battery that is the problem.

Evaluation and Adaptation of 5-Cycle Fuel Economy Testing and Calculations for HEVs and PHEVs (energy.gov)

“Hybrid System Stopped - Steering Power Low”
I got this on my dash three weeks ago when I was going to pull out of my parking spot at the mall. I put the actual hand gear in reverse, the back up camera came on, but the car remained in park and that was the message displayed. After a couple more tries of putting it back to park and then reverse with no success, I turned the car off and back on, and the message went away. It has been okay so far…
I think I have read this kind of reports on this forum and elsewhere. It might be worthwhile to check the 12V battery.
 
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I’m just dropping in to see if the wiring harness issue was common. I’ve had mine over a year now approaching 8,000 miles with no issues and exceptional gas mileage. I live in Fl & don’t pay the warm up & heating mileage penalty. The AC is electric so the gas motor can stay off when AC required and enough charge in the hybrid battery.

I’m wondering if the bad wiring harness was in a certain run of theses vans and was resolved early in production.
 

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“Hybrid System Stopped - Steering Power Low”
I got this on my dash three weeks ago when I was going to pull out of my parking spot at the mall. I put the actual hand gear in reverse, the back up camera came on, but the car remained in park and that was the message displayed. After a couple more tries of putting it back to park and then reverse with no success, I turned the car off and back on, and the message went away. It has been okay so far…
The message you got is different from the "Hybrid System Failure" message. What this message means is that the hybrid system is no longer running. This is similar to if a gas powered car stalls. There could be many things that cause this error, including the hybrid system failed to properly start to begin with. There is a computer(s) that runs the hybrid system. This computer could have failed to start up properly or is not getting power. Steering power low is related in that since the hybrid system is not operating, neither is the power steering system.

Turning the car off and restarting it is the best solution. If the problem goes away, then it might be a glitch that occurred. If the problem comes back, then there is something going on that is causing the problem to occur. There are probably a whole bunch of causes, from a wiring issue where the computer is not getting adequate power to some check that the computer makes to verify the hybrid system is ready to run.
 

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I have a 2021 Sienna Platium handicap Van. Just received message for Hybrid maintenance take to dealer. NOTE AGAIN, this is a handicap vehicle as I am a Vietnam War Vet 100% disabled. From what is stated here, Have appt with Toyota on Monday, 9 May 2022 for message so will let members know here the outcome. Can not let them have my Van over 3-4 days. Have Power wheel chair and of course got through a mobility dealer. Van has less than 4,000 miles on it. Had issue at about 1,000 miles while at a stop light, green light, went to go and nothing. Appeared van not running, put it in park, hit start and lights showed Van running on electric but could not put in gear. Of course in Florida and people were not happy with me. shut off, turned on, even called 911 for police and tried couple more times on and off and it finally went into gear and away I went calling 911 to state police not needed. Took to dealer which first told they did not work on 2021 Toyota Sienna conversion vans, in Venice Florida and finally got service manager. 12 volt battery bad plus another issue I can not think of. Mileage has not been good. 27.3 overall since then. never got over 27MPG. Not 36 MPG. Conversion is VMI and will never get a van from them again. Nothing but trouble! Cheap conversion, squeaks and groans around corners, pieces of inside conversion part coming louse. First took from dealership did not go 20 miles and we could smell smoke. Pulled over and return fuel line rubbing on tire. Dealer took it back to shop and gave us back our 2019 Pacifica limited. Dealer also found that at factory in Arizona when cutting front cowl, they cut into the AC box and water was running on floor. Cost VMI over $4,000 dollars and dealer said he had 3 more new vans with AC box cut.
As said, keep everyone updated so stay tuned!
 

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Curious if anyone else has had this happen yet? We had 2000 miles on the new Sienna when it started saying “Hybrid System Failure, Contact Dealer”. We took it in and they said the main hybrid wiring harness has a faulty connector. The problem is, they don’t have a part to fix it. It’s been sitting in the maintenance bay at the dealer for over a month now with no ETA. They put us in a 2020 rental, but we are getting pretty irritated that we paid for a new van but we don’t have that new van. I actually think that after 30 days it qualifies under our state lemon law. Wondering if it’s a one-off issue or if this is going to be a systemic problem and Toyota ends up doing a recall for this wiring harness.
Please see my response. Gary S. as of 05/06/2022
 

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Curious if anyone else has had this happen yet? We had 2000 miles on the new Sienna when it started saying “Hybrid System Failure, Contact Dealer”. We took it in and they said the main hybrid wiring harness has a faulty connector. The problem is, they don’t have a part to fix it. It’s been sitting in the maintenance bay at the dealer for over a month now with no ETA. They put us in a 2020 rental, but we are getting pretty irritated that we paid for a new van but we don’t have that new van. I actually think that after 30 days it qualifies under our state lemon law. Wondering if it’s a one-off issue or if this is going to be a systemic problem and Toyota ends up doing a recall for this wiring harness.
 

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I have a 2021 Sienna Platium handicap Van. Just received message for Hybrid maintenance take to dealer. NOTE AGAIN, this is a handicap vehicle as I am a Vietnam War Vet 100% disabled. From what is stated here, Have appt with Toyota on Monday, 9 May 2022 for message so will let members know here the outcome. Can not let them have my Van over 3-4 days. Have Power wheel chair and of course got through a mobility dealer. Van has less than 4,000 miles on it. Had issue at about 1,000 miles while at a stop light, green light, went to go and nothing. Appeared van not running, put it in park, hit start and lights showed Van running on electric but could not put in gear. Of course in Florida and people were not happy with me. shut off, turned on, even called 911 for police and tried couple more times on and off and it finally went into gear and away I went calling 911 to state police not needed. Took to dealer which first told they did not work on 2021 Toyota Sienna conversion vans, in Venice Florida and finally got service manager. 12 volt battery bad plus another issue I can not think of. Mileage has not been good. 27.3 overall since then. never got over 27MPG. Not 36 MPG. Conversion is VMI and will never get a van from them again. Nothing but trouble! Cheap conversion, squeaks and groans around corners, pieces of inside conversion part coming louse. First took from dealership did not go 20 miles and we could smell smoke. Pulled over and return fuel line rubbing on tire. Dealer took it back to shop and gave us back our 2019 Pacifica limited. Dealer also found that at factory in Arizona when cutting front cowl, they cut into the AC box and water was running on floor. Cost VMI over $4,000 dollars and dealer said he had 3 more new vans with AC box cut.
As said, keep everyone updated so stay tuned!
Have a VMI 2021 edition as well. 3,000 miles on it and it is incapacitated. Hybrid System Failure light is on. Getting it towed to dealer now. Not looking forward to their response based on what I have read about this issue. Seems to be happening to all versions of this vehicle. Not just wheelchair converted versions.
 

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Have a VMI 2021 edition as well. 3,000 miles on it and it is incapacitated. Hybrid System Failure light is on. Getting it towed to dealer now. Not looking forward to their response based on what I have read about this issue. Seems to be happening to all versions of this vehicle. Not just wheelchair converted versions.
Let's hope it's the 12V battery that's giving you grief, which would be an easy fix. I would take a couple of pix or a short vid of the problem to maybe help push back against the "problem couldn't be reproduced" posture that some "busy" dealerships like to assume.
 

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Have a VMI 2021 edition as well. 3,000 miles on it and it is incapacitated. Hybrid System Failure light is on. Getting it towed to dealer now. Not looking forward to their response based on what I have read about this issue. Seems to be happening to all versions of this vehicle. Not just wheelchair converted versions.
Have them test / charge / change the 12v battery in the trunk. It’s a false positive that comes up during startup diagnostics when rear battery in back is low (it’s like the size of a motorcycle or lawnmower battery).
 

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Have a VMI 2021 edition as well. 3,000 miles on it and it is incapacitated. Hybrid System Failure light is on. Getting it towed to dealer now. Not looking forward to their response based on what I have read about this issue. Seems to be happening to all versions of this vehicle. Not just wheelchair converted versions.
Thank You for the info. I wish you the best. With Conversion Van for disabled, it gets to be finger pointing between VMI, conversion company and Toyota. New Toyota dealership in Venice Fl told me even if Van is new, they do not work on conversions!
 
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