Hi I am new to the forum and want to thank you all for being here. I hope this is the right forum for this question. We have a 2005 Prius with 156,000 miles on it. The red triangle warning light was coming on intermittantly, our mechanic ran the code and it had a couple things come up... an evap. warning and an ABS warning. He could find nothing wrong with the car. The brakes were fine but he did suggest we replace the gas cap (we did). The light did not go way, rather it stayed on contunuously. Our mechanic referred us to someone who is more familiar with the Prius. The other mechanic did diagnostics and could find nothing wroing. He did however say that he saw something unfamiliar to him regarding the computer system. He said it appears there is an expiration year (2022) of sorts, for computer updates, he had never seen this before and we have no idea what that even means.. I know there are numerous computer systems in the car and he did not specify. He reset the light to off but said it would likely come back on. it did. The car runs really well and the batteries are good but I don't feel safe driving it with that light on. Any thoughts or suggestions would be helpful.
There are a couple possible reasons for the "master warning light" coming on (red triangle of death). The driver's door switch could glitch - if the car is in gear and the door is "open", the warning light (and a "shift to park" message) will turn on. You should also see the red "door ajar" light come on the dash. The engine oil could be low. If oil pressure drops because of that, then the RToD (& a oil pressure icon) will appear on the MFD center screen. Or there's a fault code in the HV battery or hybrid control ecu's. It wouldn't surprise me if a repair shop didn't have a capable scantool to check all systems on a Prius. Here's a thread that reviews several apps and devices for smartphones. Some are "all system" capable. Posted via the PriusChat mobile app.
Oops! Managed to overlook the "missing link". The Autel AP200 is being replaced by the AP2500 or AP2500E. I don't know exactly how well the new one works. https://priuschat.com/index.php?posts/3290690 Posted via the PriusChat mobile app.
No resolution yet on this warning light. It went off again for two days and came back today. Stayed on for about ten minuts then off again. Oil is full and no "door ajar" light. The second mechanic who ran the diagnostics and could find nothing wrong said he has a new $15,000 machine and it is very thororough. He seems honest and was well reccomended. The only thing left that I can see is to go to a dealership and have them run tests although I won't go to the one closest to us as they are crazy expensive and I don't trust them. Can anyone reccommend a trustworthy Toyota dealership in Massachusetts? Thanks!
trustworthy dealership is an oxymoron unfortunately. if you want to check for codes, ask them how much up front. idk about the 15k machine, it may or may not pull prius codes.
Hi again, The red triangle mysteriously dissappeared since my last post. It did come on a couple of times very briefly but then went off again. Now it is back, all the time. The mechanic who said he could find nothing wrong with the car told us that when the code was written for the diagnostics it had a 2022 expiration date. Our car is a 2005. I have no idea what that means and my husband was unclear also. The mechanic implied the car was fine to drive but I do not trust that, my husband is still drivung it. I am including the original code. Any thoughts would be appreciated.
Given the context of that diagnostic report, I am changing my opinion of what the master warning light is doing in this case. The ABS code C1256 indicates a possibly very serious fault with the brake system and the RToD is letting you know how serious.. When you step on the brake pedal, the hybrid control ecu decides how much regeneration braking vs how much normal friction braking to use. Unlike a conventional car, your foot has no direct connection to the brakes at the wheels. The friction brakes are controlled by the ABS brake control ecu. It has a pump to pressurize brake fluid to over a thousand psi and stores it in an accumulator (a special pressure tank). The ecu uses valves to direct the pressurized fluid and apply the friction brakes at each wheel. Normally the pump runs a few seconds to "charge up" the accumulator. As you use the brakes a few times, that store of pressurized fluid is "exhausted", and the pump runs again to recharge things. So, at a low pressure value, the pump turns on, and turns off at a high pressure setpoint. C1256 means that even though the pump runs awhile, the fluid pressure never gets up to the high pressure setpoint. There is likely a leak inside the brake actuator assembly that lets the high pressure "bleed off" (not an uncommon fault on a Prius). Eventually the pump runs "all the time" and can wear out. If (when) the pump fails, braking function is severely compromised. I would suggest not driving the car until it is properly diagnosed by a shop that understands hybrids and their unique problems. Posted via the PriusChat mobile app.
