Hybrid System Failure Icon

The other day, I was driving my 2006 Prius on I-20 in Shreveport. As I came off the exit and approached route 80, my navigation display read “PROBLEMâ€, and the car suddenly coasted to a stop. All of this occurred in about 100 feet, so I was lucky to be able to coast the car to the shoulder, because it just died where it stopped. If this had happened while I was on the highway, my whole family would have probably been killed, as there was no way we would have been able to safely get out of the way of the multitude of semi trucks that drive that road.

I attempted to re-start the car, and the red triangle warning appeared on the display, along with the little car with the exclamation point in the middle of it, otherwise known as the hybrid system warning icon. Needless to say, the car would not turn over.

I immediately called Toyota to see if they had any info to help get the car going. Toyota was absolutely useless, and the customer service agent said the only recall showing on my model was a floor mat recall. I told him that I knew he was only doing his job, but it was a shame Toyota actually believes Americans are stupid enough to believe the floor mats are the problem. Luckily, we had AAA, so the car was towed home, after a two hour wait.

Diagnostics:

I checked all fuses and relays, checked battery connections, and saw no apparent problems.

I knew I had not changed the oil in quite a while, so I decided to clean the throttle plate, in case the sensor was dirty. I picked up some throttle plate spray (safe for the Prius sensor), checked the spring tension (Big spring under the air filter housing has a tab that can be pushed to check tension, which was ok), and cleaned the throttle plate and sensor. No change.

Next, I put my meter on the 12V battery terminals, which read 12 volts.
The Prius manual states that 12.6 volts is considered “chargedâ€.
It is also required to switch the relays and crank the engine.
Less than 11.9 Volts is considered discharged.

I put a charger on the battery and left it on overnight. When I tested the battery in the morning, it read 3 volts, so I knew the battery was bad. The charger I used, has multiple charging modes, including one to boost the car. I ran the trickle charge on 2 amp charge overnight, but switched the charger to medium 8 amps, to see if the motor would crank over. It did not, so I knew there was another issue, as the car should have turned over when boosted.

I decided to have a look at the Hybrid battery.
I lifted up the carpet covering the top of the battery. I immediately noticed an orange service disconnect mounted on the left side of the battery. The disconnect has an orange handle, that has to be lifted slightly to unlock, and then rotated horizontally to the left. The entire disconnect pulls out, and a sliding cover hides a 125 VDC fuse.

I checked the fuse with my meter, and sure enough, it was bad. My car is four years old, with 130,000 miles. It was an extremely hot day, so it could have blown for a number of reasons. I had not heard any noise when the car broke down, so I don’t believe there was a short, as a 125 amp fuse probably would have made some noise.

I called two Toyota dealers in my area, the first wanted $208 for the 12V battery and $120.00 for this fuse!!! The second wanted $167 for the 12V and $87.50 for the fuse, which was still outrageous. I really didn’t want to waste $87.50 plus tax, on a millisecond test of a hybrid battery fuse, so I decided to see if I could locate a similar fuse to test with. A typical buss fuse runs from about $3.00 to 30.00.

I went to over a dozen electrical supply stores, including a commercial electrical supply, Home depot, etc. There was nothing even remotely similar to this fuse. Figures, Toyota would make the fuse proprietary, just to squeeze a little more cash out of us. I was concerned that using a replacement fuse could cause an arc, and cause damage to the battery, or blow up in my face etc. In the end, I decided to be safe and just buy the Toyota fuse and battery.

I installed the battery and fuse, and the car turned on. The idle was fluctuating, so I decided to drive it just to stop it from stalling. In hindsight, I should have just kept it in park and mashed the gas pedal a bit, but I was just happy to see the car start. The car drove a few feet and then stalled, and would not turn over again. The display allowed me to put the car in neutral, so I pushed the car onto my car port and hooked up the charger, just to check the new battery.

It had probably been sitting in the sealed box for a while, because it showed 12.5 Volts.
I put the charger on medium charge, which boosted the battery voltage to 13 volts, then tried to turn it over. The car turned over! I turned off the charger and let the car run for a few minutes until the engine cut off. I had to hit the gas a few times to keep the engine running.

Then, the car began to “push†while in park, with the emergency brake on. (It was acting like it was in gear) A warning light came on my Nav display: “Problem Transmission P Lockâ€. The car was definitely in park, so perhaps the electronics had been stuck in drive, or the park button was not fully engaged.

I believed the brake pawl may have been sticky from being towed on the flat bed, worked on, electrical problems etc. So, I turned the car off and on, and the pushing stopped. I put the car in neutral and rocked the car back and forth a couple of times to see if the parking pawl was stuck, turned the car off and then on again, and the problem went away.

I knew my oil was dirty, so in order to keep the sensor clean, I flushed and changed the oil, changed the oil filter, and then topped up all fluids.

After that the car started without a problem, so I drove around the block a few times, cautiously stepping on the brakes to recharge the hybrid battery. I took the car on the road today and drove about ninety miles, and it had no problems.

The funny part was when I took the 125 amp fuse to my Toyota dealer, nobody in the place knew what the fuse was for. When I told them it was out of their Hybrid battery, the technicians told me they had never seen that fuse before, and didn’t even know the Hybrid battery had a fuse!!!.

I can only imagine how many hybrid batteries have been replaced at the customer’s expense, because technicians didn’t check to see if a fuse was blown!

Summary:
Check all fuses
Check 12 V battery for 12.6 volts
Check Hybrid battery fuse
Check Throttle Plate and sensor for sticking spring or dirty sensor & clean if needed
Boost battery if needed, to start engine
Top up fluids
Make sure parking brake and parking pawl are not sticking to cause warning

 

So far the battery and car have been running well, other than the A/C issues which I have addressed on another post.

When I was diagnosing the car, a Ford mechanic friend of mine came over with his computer code reader, and tried to get a code by plugging it into the car. When the battery failed, it may have cleared the codes because none were present. Other than that, he couldn't help with the Prius.

I did replace the 12V battery and the fuse at the same time, because the 12V had discharged below 11V.

Great news on the toyota parts cheap site! I had a feeling the dealer was over charging, but at the time I had no other options.

I will keep my eye on the inverter for the future.

The great thing about this site is that people may have similar issues resolved in a different way. There is a wealth of information provided by members, that just won't be offered by the dealer.