Auxiliary Battery Failure

Auxiliary Battery or Inverter Pump Failure?

A few nights ago, I was about to take the 05 Prius (53,400 miles) to fuel it up after my 16 years old daughter arrived home from her summer job. She pulled in the driveway and left the car on. I got in and noticed that a warning light just illuminated. It was the VSC light. At that time, the car was on for about half an hour and driven a distance of about fourteen miles. The air temperature along the drive ranged from the low 90’s at her starting point to just over a 100 at home. I started driving. Within a couple hundred feet, I noticed that the air conditioning was blowing hot air and that the Master Warning light, the Check Engine light and the ABS light were on as well as a red car icon with an exclamation mark through it on the MFD (Hybrid System Failure as I found out in the owner’s manual).

I stopped and turned the car off and on several times to see if the problem could clear up. It did not. I decided to take it to the dealer the next warning, but did not want it to be very low on gas. A mile into the drive, after making a right turn, the car lost power (shifted into neutral) and a message displayed on the MFD to the effect that the parking pawl was abnormal and that the car had to be parked on level surface. I could not shift the car out of neutral or turn it off. Finally, after pushing and holding the On button for a few seconds it turned off. I waited a while and turned it back on and continued on my way. It took a couple more power losses and restarts to get to the gas station which was about two miles from home.

As I was pumping fuel, I called the service department. They just closed. I called Toyota Roadside Assistance, but it was going to take an hour to get a tow truck. Since the car was outside the initial 3/36 factory warranty, the tow was not automatically covered, even though I have the 7/100,000 Platinum Extended Care Plan. I told the Toyota rep that I’d use AAA. I did not want to leave the car overnight at the gas station or outside a closed dealership. I asked if it was safe to try to limp home. He assured me that it was safe if I felt safe driving it.

I started driving home. All of a sudden all the warning lights were gone and the car drove normally. The air conditioning was blowing cold air. About a mile from home, the warning lights and message reappeared. It took about half a dozen restarts to make it home.

I had AAA take the car to the dealer the next morning on a flat bed truck. The car started right up to drive up the truck’s ramp. The mater warning light flashed on and off once as I turned the car on.

The diagnosis was that the auxiliary battery shorted out internally and resulted in low battery positive charge (code C1241) and low power supply voltage (Code 2318). I was charged $460 for a new battery and labor charges for installing it and clearing all the trouble codes and stored memory codes. Because the failure was attributed to the auxiliary battery, none of the labor charges were covered by the power train or hybrid system warranties or the Extra Care Plan.

The warning lights returned the day after the repair, as my daughter was on the way home from her summer job at the UCLA Medical School. Fortunately she was only ¾ of a mile from home, off the freeway and away from busy commercial traffic. She freaked out and pulled over. She is not sure if she lost power. She does remember seeing the master warning as well as the Check Engine, VSC and ABS lights and the Hybrid System warning icon.

We went to get her and I drove the Prius home.

Yesterday morning, I drove the Prius to the dealer. The drive was unremarkable. The Master Warning red triangle with an exclamation mark and the Check Engine Light were on.

This time, I was told that the cause was inverter cooling system failure caused by a Hybrid Inverter Pump internal failure (code P0A93).

At least this repair was covered by the 5/60 power train warranty.

I asked to be refunded some of the labor charges from the previous repair. The dealer insists that the two problems were totally unrelated and that the pump failure code did not appear after the first episode. OK, I was shown three pages of codes printed after the initial repair. Can’t say that I went through the list with a fine toothed comb, but I’ll take their word for it. Only one code showed up on the printout from the second repair.

I simply cannot understand how similar problems, at similar points in the drive, under similar conditions, two days apart are not related.

As a good will gesture, they offered to comp the next minor service on the Prius or the Camry Hybrid.

My questions are as follows:

• Why would a weak or shorted aux battery cause a low power supply in the system when the car is running off the HV battery and the 12v system is powered by the inverter for almost as long as an hour? After all, the battery was strong enough to allow the SKS system to function and to start the car. Can I really accept that it was really the root cause of the initial failure?
• Isn’t it more likely that the low power supply was caused by an overheated inverter than by a failing aux battery?
• How do I go about proving it?

Thanks.

 

I was shown the three pages list of codes from the first repair. I did not personally go through it; it was too overwhelming. That being said, I doubt that they would lie to me that the P0A93 code was not present while at the same time showing me the list.

That was the original 12v battery. The car's production date is 08/15/2004. I am sure it was due for replacement. We have seen intermittent signs of a week battery. Weird beeping after turning the car off and refusal to lock or unlock with the SKS (mostly solved by the replacement of the fob battery). If there were newer or more persistent symptoms, my daughter has not told me of those. She has been the Prius' primary driver for the past year. I do know that she sat in the car for an extended period of time, in the Acc mode, about a week before, participating in some survey conducted by GM engineers. I cautioned her never to do that again. The car performed normally for the next four days before the problems started.

On the day the car started acting up, I had no trouble rebooting it numerous times when it kept stalling and displaying the parking pawl messages as I was limping home.

It is a large dealership with a well reputed service department. It has many master mechanics who are well trained to work on the Prius. I have a service adviser I trust. Unfortunately he was on vacation last week. My crisis of confidence started when the guy who took care of me, tried to sell me a new air filter and a new a/c filter when he called to give me the diagnosis and the repair estimate. The car was in just three weeks earlier for a routine service and underwent a 27 points inspection. My skepticism only got worse when a nearly identical problem developed the day after they fixed the initial problem.

Based upon what you and gbee42 have written, I can accept that this was an unlucky coincidence.

Thanks

 

The battery itself was $189.33 including Los Angeles County usurious 9.75% sales tax. I was charged 2.5 hours of labor for installing the battery and clearing the codes.

BTW, last year just before the economy tanked, when my daughter got her driver's license, I got suckered into a fully optioned '09 Toyota Camry Hybrid. My daughter now drives the Prius. That is party the reason that I am so upset that a previously very reliable car had two similar break downs in such quick succession.

Well, the way it was explained to me, they actually had to re-flash the computers, much as they did during the recall a few years ago. I recall that Toyota paid the dealerships for several hours of labor to perform that repair. Do you have any documentation from Toyota that shows that the trouble codes, literally dozens of them, can be cleared in a mere three minutes?

I did raise a fuss. They gave me $90 credit against my next service. I'll make sure it is used against the 15,000 service on my Camry Hybrid.