Revive my dead Prius

A simple bluetooth OBD scanner for $15 and an app called torque for $5 is enough to diagnose just about any hybrid related issue on the Prius. You will need a code scanner to make any heads or tails of what's going on. Transmission "locked up" sounds like a bad diagnosis, I would completely disregard and seek a different opinion.

Prius starter battery is the hybrid battery, the 12 volt battery only powers on the systems in the car and energizes the relays to complete the circuit between the inverter and the high voltage of the hybrid battery.

What is the history of the car? Where did it spend the last decade? How long has it been sitting unused?

 

If the headlights turn on nice and bright with the car off the 12 volt battery path is probably ok. No head lights its probably a dead battery. I did not understand your last statement about the battery post and 16 volts. if you have no real experience troubleshooting a cars 12 volt problem don't start on a Prius. Bad things can happen around a dead 12 in a Prius. The cars electronics are easily damaged.

If no headlights just go buy a new battery and carefully install it. Its probably sat for long period stone dead which will kill a battery..

 

The 12 Volt battery is not the starter battery. It just powers up the computer electronics and closes the high voltage relay so the large traction battery is able to power the motors and start the engine if needed.
Are there any dashboard warning lights lit? Does the car boot up to READY mode?

 

You don't need any "codes".

IF the voltage reads "nothing" when measuring from one battery post to the other........the battery is dead and you need a new one.

That small battery on a hybrid does NOT turn the "starter". It just boots up all the computers.
And it should be around 13 volts, not 16.

 

whats the mechanics name? 3 hour drive wow

 

Things are done differently in TX for sure.

Did the mechanic use a laptop and connect it to the OBD2 port on the Prius? He should have used Techstream which is a computer program, specific for Toyotas.

Are you sure about the mechanic's qualification and reputation. By definition a mechanic should be able to fix the problem; that's his occupation and training. The owner likely will not like the diagnosis, because of the cost to affect a repair. Its one thing if he doesn't have the tools/parts on hand to affect a repair, but to say not repairable. If he said the transaxle needs to be replaced, that would have been more believable, b/c that would have been a diagnosis. Albeit, one you would not like, and one you would question and hopefully want a second opinion, esp given 43,000 miles (if the odometer is accurate).

Call Matt at Texas Hybrid Batteries (serves the DFW area). Likely more capable or will know far more capable mechanics.
Texas Prius Battery Replacement

Surprised no one asked: 2008 with 43,000 miles.
Mileage is suspect. Did you buy this car from a grandmother who only drove to church, the grocery store, and doctors office, all w/in a 3 mile radius of her house?

2017-2008 = 9 years.
43,000miles/9years = 4,777 miles/year = 398 miles/month = 91 miles/week = 13 miles/day​

Did you pay for a car fax report?

Are you aware it is easy to get another odometer that has lower mileage or get the odometer reprogrammed?

 

Hehehe! You're such a funny person. Drive to church or grocery store? Yeah, maybe that's what had happened.

Odometer may have being rolled back

 

There are some legitimate low mileage vehicles but you wonder why they sold it.
I have a 2000 Tundra with only 56K miles, for instance.

 

Yeah, some of them may have being sold, because probably, financial needs, or just owners wanted to change to something else

 

Other scan tools can access HV battery also.

 

Agreed. An ultra low mileage may be legitimate if the situation backs it up:

• Gradma going to church, grocery store, doctor office.

• Multi-vehicle household where the truck is used as a toy hauler and occasional pickup at Home Depot/Lowes for a large item.

​

• Wealthy household with more vehicles than they can ever drive and put a ton of miles on.

Hopefully OPs situation is truly a low mileage vehicle and not a fradulent odometer rollback or low mileage combo meter swap.

 

Thanks for the recommendation @exstudent. Unfortunately I was the "respected hybrid mechanic" that diagnosed the car.

I have a basic order of troubleshooting that I use every car and it goes like this:

-Check the 12 Volt battery and replace if low. In this case the aux battery was at 11.5V (dead) so I swapped it out with a good one.
-The car still wouldn't power all the way up so I checked all fuses and relays. All good.
-The only ECU that I could get to power up was the HV Battery ECU but the main SMR's would not close. These were the DTC's:

-P3108 and U0146 which are basically just communication errors because other ECU's were not powering up.

-In the process of trying to figure out why systems weren't getting power I went ahead and checked the block voltages on the hybrid battery. 10 of them were right at 14 Volts and the other 4 were somewhere close to 13 Volts. I've seen this exact scenario many times before and it was always caused by a seized drive train. Basically what happens is the owner tries to start the car over and over and each time it drains the battery more until you finally reach a true 0% SOC which is much lower than the computer would ever allow. Typically to get to this point the 12 Volt battery has to be disconnected multiple times in order to trick the BMS into draining the pack down lower.

This was the point at which I stopped fooling with the electronics and just went old school. Get a ratchet and a socket and crawl under the car and try to role the crankshaft by hand. I've seen no less than a dozen seized engines over the years because people don't add oil. When engines seize you get zero crankshaft movement, in this case there were a few degrees of movement in each direction but absolutely nothing more. Further evidence of a transaxle mechanical failure was that the entire bottom of the transaxle was covered in a thick oil and dirt residue and the underside of the engine was nice and clean.

If the op wants to confirm this diagnosis all he needs to do is drain the transaxle fluid. If there's less than 3.5 quarts or it looks/smells like burnt motor oil then it's done. My guess is that the trans was serviced and they either put traditional ATF back in (seen that before) or they forgot to tighten the fill plug on the front of the unit and it fell out.

I hate giving owners bad news especially when it's a problem that I can't fix. While I have replaced a number of engines and transaxles I just don't have the time to do it right now. For this reason I decided that I didn't want to charge these guys for my time and since I was working for free I didn't want to stay to confirm a diagnosis that I was almost sure of.

My advice is never ever ever buy a Prius that won't start.

Hope some of that helps,
Matt

 

I like that grandma grocery store .....statement. Hehehhe

 

Wao! This is great. If you've got some spikes and dirt combined under the that trans axle, there must be some terrible fluid leaks. Just as you've confirm.ed rotating the crankshaft pulley, to come to that conclusion, I'd have suggested you rotate it 360° that would give a more definite answer.

I have a ??? here:
Isn't the SRM, powered by the 12volt battery, in order to engage the HV system?
I'm trying to see how a failed transmission system would not cause a car to start.

Does the READY light come on?
If the aux battery was replaced, and the car didn't start, my next try would be to check the 12volt wirings from the battery, straight to the inverter assembly. If all those wires checks OK, would say the inverter is fried up!

 

Get the car scanned, and let's see what you come up with.

 

Answers in post 13

 

Seen! Thanks

 

Spikes? 360°? If it rotated a full turn (as it should) this would mean that it was not seized. I don't think your understanding something here.

I know your an automotive engineer or something and your trying to learn all you can about the Prius so you've definitely come to the right place. There's a ton of good information on PriusChat, read more/post less.

 

In a Prius, there is no separate starter motor. The transmission is what cranks the engine over to start it. If the transmission is seized ... nothing is going to be starting that engine.

But the story left me with a question too. The motor-generators have position resolvers on them to detect rotation (very precisely, to about a 4096th of a revolution, IIRC). If the ECU sends current to the motor and nothing turns, it is going to know that right away, set the corresponding codes, and not make a prolonged, battery draining attempt to make stuck things move.

For example, a Gen 1 (just because I have the paper manual handy) can give you four different P3120 INF codes to tell you the shaft is damaged (239), MG1 is locked up (240), the torque limiter is slipping (241), or the power-split planetary gear is locked up (242). I don't have the Gen 2 codes handy and they may be different, but you get the picture. It isn't that there's no other way to diagnose the car besides reading the codes, it's just that reading the codes is darned fast and doesn't get grease on your shirt.

In a more typical no-start engine (because of fuel or spark problems, say), where the ECU will use battery power for 15 seconds or more at a time to spin the thing hoping it starts, I certainly worry about draining the HV battery, as every one of those attempts seems to take the state of charge down by 1 or 2 percent if I remember right. But in a situation where the ECU is going to immediately detect nothing moves, give up, and set codes, I'm struggling to guess how many repeat attempts would need to be made to really drain the battery much.

-Chap