I am one of those Prius repair guys that have to find a solution to every problem. Most of the issues that I have encountered with the fuel saver have been relatively easy to repair.
I recently came across a Gen 2 Prius that threw me for a loop. It would not store trouble codes, but it would intermittently set the master warning light and say "problem." I had to get to the bottom of it, and here is what I did to solve the problem.
Intermittent Master Warning Light: Solved
The master warning light can come on for a bunch of reasons. Usually, though, it comes on and stays on. So for the light to come on and off randomly.
I observed the issue for several days, with a scan tool hooked up. There were no codes, but one thing tipped me off that led me to fix the problem in just a few minutes.
When the master warning light would come on, the display screen would say issue. Some of the time, though, the oil pressure warning light would be present. I figured this was normal since the engine shut off whenever the master warning light was triggered, no engine running, no oil pressure, right?
Suspecting there was a root cause, I began digging around. After being in this industry for 15 years, I have learned a thing or two about checking the basics. I started with the most obvious stuff under the hood.
I found the engine oil was low and added a quart as any good tech would. I checked the coolant level on both sides, normal. Transmission fluid, normal, and everything else I checked was fine. I was stumped at this point and hungry, so I went for a drive to get lunch.
Can you guess what happened next? I went to lunch with no problems. No master warning light, no "problem," and no intermittent oil pressure light.
Conclusion
The culprit was nothing more than a low oil level. I reminded my client that checking the oil level every time they fill up on their high mileage Prius will save them from an even more expensive repair bill.
So if you are experiencing this issue, do yourself a favor and check that engine oil level before spending time and money on something super simple.
That is all for today. I look forward to seeing you in the following article. Camry hybrid owners are having brake pump failures.
Check out this wild new battery tech that Tesla has and why it will forever change the auto industry.
Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporters.
Tags:
- brake
- brake light
- check engine
- engine trouble
- hv battery
- hv battery fan
- master warning light
Joined:Apr 5, 20171000Location:TorontoVehicle:2006 PriusModel:II
Certainly looks like a hybrid battery issue.
If Hybrid Battery is not working properly, the regenerative braking system is unable to put energy back into the hybrid battery. So the brakes feel different.Start gathering your money for a replacement.
Joined:May 11, 200599,22244,9580Location:bostonVehicle:2012 Prius Plug-inModel:Plug-in Base
clean the cooling fan, 12v looks weak too. how many miles on her?
I'm not saying it isn't the traction battery. It may be going out. But, as @bisco said, 12.0 volts on the aux battery is pretty low with no load and that can give you all sorts of codes.
Joined:Apr 5, 20171000Location:TorontoVehicle:2006 PriusModel:II
It has 150,000 Km. How would I know for sure if it was the 12V battery causing the issues vs the traction battery (without installing a new one)?
As well, when driving the battery on the display seems to fluctuate between 4/5 bars and full. It is never dropping below 4 bars. Is that any indication of it being 12V vs the traction?
Will clean the cooling fan and see if that helps.
Thanks,
GJoined:May 11, 200599,22244,9580Location:bostonVehicle:2012 Prius Plug-inModel:Plug-in Base
no way to know. it does seem like the hybrid, but low voltage to the computers can wreak havoc. if you are saying that you don't want to replace the 12v, because if it's the hybrid battery, you're going to dump it, i understand.
Joined:Apr 5, 20171000Location:TorontoVehicle:2006 PriusModel:II
Don't want to dump the car. Just don't want to spend $200 to find out it is the traction battery and then pay another $750 on a refurbished traction battery.
Joined: May 11, 200599,22244,9580Location:bostonVehicle:2012 Prius Plug-inModel:Plug-in Base
if you're going to keep the car, and 12 volts is an accurate cold measurement, you'll be replacing the 12v anyway. any idea how old it is?
Joined:Apr 5, 20171000Location:TorontoVehicle:2006 PriusModel:II
The 12V is at least 4 years old.
Joined:Jan 16, 20174912960Location:Lincoln, NEVehicle:2017 Prius PrimeModel:Prime Plus
Load test your 12v battery....measure of voltage is not the way you should check your battery health
Posted via the PriusChat mobile app.
Joined:Feb 13, 20171701130Location:SeattleVehicle:2005 Prius
I have read that as a preventative thing, you should replace the 12V battery every 4-5 years. Older 12V batteries can throw codes at you that might not be true.
This is very subjective and should be taken with a grain of salt, and very much depends on the operating environment and how well the battery has been maintained. I find it hard to throw out a perfectly serviceable battery just because some arbitrary time limit has passed. Test the battery and if it is not up to snuff, replace it.
It is not really that they are not true, and it is not until you look at what caused the code to come up, you probably find one of the things the computer is not happy about is the low voltage on the 12 V supply.