Check hybrid system


Asked by Jul 16, 2017 at 11:12 PM about the 2007 Toyota Camry Hybrid

Question type: Maintenance & Repair

2007 Toyota Camry Hybrid
My car started hesitating when giving it gas, and
Toyota the Toyota dealership said I needed a new
hybrid battery pack. I took the thing apart myself
and found one bad cell, and ordered a new cell
from Amazon for $40. I ohm'd everything out and
checked the voltages after connecting the string
back together. 263v.
But now the car won't start, and I'm running out of
ideas. The power locks work and headlights turn
on, but break lights do not work and power seat
does not function. The dash lights turn on when I
use the push start and the display says "check
hybrid system". My next option is figuring out the
control wiring and sensors.
I do not have a scan machine.

15 Answers


While I can't specifically answer your question I can tell you this. Hybrid batteries sell for upwards of $1500 in most cases. They are also deadly!! If not handled properly you can literally be killed trying to replace or repair the system!! You should find out what the normal operating voltage should be and go from there. But proceed with extreme caution and only if you know what you're doing!! I doubt that what you bought for $40 was a hybrid battery!! HTH. -Jim


The entire pack sells for that amount and more, but inside there are 34 individual batteries connected in series. The cell I bought has a good voltage and is an exact replica of the battery cell I replaced. I understand the risk associated with opening it up and work on battery strings with a much higher voltage on a regular basis.

1 of 1 people found this helpful.

Knowing what trouble codes are stored in the computers is key to diagnosing a Hybrid System. Since you cannot start this vehicle and take it somewhere for further diagnosis try disconneting the 12 VOLT battery for about 10 min. Reconnect and let's see what happens? Are you sure there where no sparks while you were performing this repair?

1 of 1 people found this helpful.

I reset the maintenance through the dash and took off the battery connection for 10 minutes, with no progress. I tried plugging in an OBD2 and it does not connect. I figured out there is no power to the port to check the codes. I pulled all of the fuses I think could be related under the dashboard. After some research and trouble shooting I narrowed it down to the fuse bus bar under the hood. The 120amp fuse blew and the fuse box must be removed to access the bolts underneath that hold the fuse down. To access I had to remove the air box and the inverter. It was very time consuming, and I got it out. Picked up the new fuse from the dealership today for $24. Will update when I get it installed.


WOW...I'm impressed with your persistence. nice job with your diagnosis. What worries me is what blew that 120 amp fuse? That is a big spark. One could weld 1/4 inch steel plate with that current. May I suggest you use a lot of caution when installing that fuse. Check both sides of where the fuse plugs in with a Volt Meter. Make sure both ends of that fuse connection is at near ZERO volts. I she blows might consider going back to square one. A pair of electrically insulated gloves might be in order. If you do get into that HV Battery Pack....look for corrosion among hose module connections. Rather common cause for Battery Pack replacement. Keep us up to date on this interesting issue.


The new fuse is installed and the car started up. I still have a check engine light, but was able to use the obd2 scanner and get the codes. The check engine light was on before I started this project. The car sat for a week with the batteries disconnected. (P0441)The first code is for the evap system which has a lot of scenarios to fix it. I will work on that later. The second code (P0A9E) hybrid battery temperature sensor "A" circuit high. When installing the battery pack one of the sensor wires came loose on the bottom of the batteries, so I believe that's my issue for the alarm. As for the fuse, I have class 00 gloves and a multimeter along with insulated tools all rated at 1000 volts and a 40 cal arc flash suit. I checked the copper bus ends on the fuse and the incoming wires. Everything was dead before handling and taking apart. The batteries were also disconnected, LOTO. As for the short that blew the fuse, the black wire that comes from the negative pole on the 12 volt battery and gives power to the components inside the hybrid battery shorted with ground. The connector they were fastened to was twisted a little and not properly placed within the hybrid battery pack. It is a small white piece of plastic connected to the frame. The car has charged back up with normal driving and runs fine. When starting the car the first time after the fuse installation it took a few minutes to get all of the components back online. Now that I took it apart once it will be much faster if I ever have to do it in the future (my sister has the exact same car and hasn't had maintenance on the batteries yet). My only regret is not getting pictures of all of the dissembling, but when working in the engine I had grease all over my hands and did not want to touch a camera or phone. I'd be happy to assist if anyone has similar issues with their hybrids and has questions. Glad I did this repair myself.


U RAA...AND GOOD FOR YOU. Keep us up to date on your continuing adventure with this vehicle. Concerning that battery temp code. I seem to recall a Toyota service bulletin concerning cleaning a dirty HV Cooling Fan. Good Job...and ...Good Luck.


Thank you, I'll look up the service bulletin.


Aaron....any updates on this vehicle?


The Camry started hesitating again during normal driving, so I assumed another battery cell probably failed. After taking everything apart and testing each battery individually the voltages were about even. The only way to find the bad cell would be to test under load and check the resistance of each battery. Using a alber cellcorder I was able to narrow down the batteries causing the issue. The car is running as normal and no warning lights on the dashboard.


Once very impressed with your persistance with the repair of this vehicle. We are all learning from your experience. Did you perhaps notice any CORROSION at the individual battery cell connection. As you most likely know..corrosion....not only causes resistance to current flow....but aslo Heat. There is a seperate cooling system for that HBP. Another Toyota Service Service Bulletin indicating cleaning procedures..


Btw...another thought. How would one Load Test each battery cell to help with the diagnosis and testing of same? With a 12 volt battery the rule was...load the battery to one half the Cold Crank Amps indicated on said battery. ....for about 5 seconds. Terminal Voltage should should hold at no less than 9.5 volts.


There was very little discoloration on the copper plates that link each positive and negative terminal, the first time I had it apart. All of the terminal posts looked clean, but I used a wire brush and clean cloth to give the posts a quick clean while I had it open. As for the copper plates, I soaked them in white vinegar for about a day or two and then gently sanded them each down until they were smooth and shiny. I wiped them off with a wet rag to clean any remaining particles or residue and dried them before rebuilding the battery pack. The cooling system works well with all vents clear and fan spinning freely. I did wipe them out with a microfiber towel to get any dust that may have made it’s way in there over the years and during the dissecting and reassembly. If you test the batteries individually you can use any machine that would use a 12volt battery, and connect with alligator clips that are rated properly. Or using the appropriate meter just test each batteries resistance across the terminals. You’ll be able to tell which ones are bad by comparing to the average number of the rest of the batteries. The bad cell will have either a really high number (most likely) or a really low number compared to most of the cells in the HBP. Thank you last_chance_garage.

3,060 it. Nice job. Keep in touch with futher updates. Thanks for the tutorial....LCG


Will do.

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