just looking for some help if anyone has some insight. My wife's Prius is 2008 base model with no real issues till just this winter. A couple times when she has tried to start the Prius the vehicle dash lights up with ABS/VSC and a soft brake pedal. Then she will shut it down and then restart again and then the vehicle seems fine and only light is READY as if nothing happened. I have not been able to reproduce this despite many tries and I did take it to Boulder Hybrid which is a Prius shop but they had no luck finding any codes with Techstream. This Prius has been our only reliable vehicle so it has become a big deal as we are not sure when this ABS/VSC light will come on again. It could be the ABS module which sucks because its expensive and hard to get too but I am not hearing it cycle which I have heard is a sign. Few questions, what other things can I be checking? Rear brakes? Wheel speed/ABS sensor? Stop light switch circuit? And is there place to get bootleg Techstream and dongle? Ideally I would like to run Techstream if I can get this ABS/VSC to happen when I am around and see if any codes may highlight the issue, that's the goal anyway unless visual inspection finds something obvious. Any help appreciated and happy holidays to everyone! My kids loves the Christmas season! Scot
If any codes were set by the ABS VSC traction control system believe me they would be stored you would not have to wait till the lights flickered one time to see what was up The light does not need to be illuminated to set codes in other words. So if there was a serious problem it would be saved for a text dream or a good ABS code reader to read so next that leads me to the 12 volt battery as always is it solid will it pass a load test etc does it show about 12 volts after sitting at rest for about 6 hours New test it with a simple voltmeter these things can make the world of difference in the Prius does your trunk leak do you have the classic signs of trunk leak like real dirty battery tray area real dirty under the spare tire like water has collected there run through that area before etc how did the terminals look on your 12 volt that can have a lot to do with voltage moving and can wreak havoc on the computers in these cars Good luck
Hello and welcome to PriusChat! So, I trying to think of any fault on a Gen2 Prius that would result in a low - soft brake pedal. I suppose it could be possible that the brake Master Cylinder is intermittently "leaking internally" (bypassing). That would make the brake control ecu sad because the master cylinder pressure sensors would not read correctly & wouldn't jive with the pedal stroke sensor. But that's a WAG. You want some codes and testing to back that up. MC faults do occur but have been REALLY infrequent for the past 20 years or so. I haven't heard of the actual MC itself failing on a Gen2 Prius. (PS - check your brake fluid level). If you want Techstream, ebay and amazon are two sources for bootleg versions, but can be sketchy to make it work (and the cable can be problematic). Use the search function to look for threads about Techstream in the forums here. Another option is to read the scantool app and device review thread at the top of the Gen2 Technical Discussion forum. These can turn your smartphone into a scantool. Some are limited and can only get some codes and some data on some ecu's. Others are more capable- codes and data from all 15 or 16 ecu's on a Gen2, plus some can retrieve sub or INF detail codes, datalog, perform bidirectional control tests, or perform service procedures such as bleeding the ABS brake system. One is very close to the complete functionality of TechStream. https://priuschat.com/index.php?posts/3290690 Posted via the PriusChat mobile app.
Awesome thanks for replies! Yes I did suspect 12 V battery. I had replaced it a year ago when the prior one completely failed. It was a NAPA battery still under warranty so I replaced the 12 V battery two weeks ago and thought that solved the problem. Unfortunately this ABS/VSC light issue is back so I don't think its the 12 V battery. I checked it again yesterday to make sure all connections where tight which they were and my Fluke multimeter shows 12.6 V so I think battery is good. I will read that thread but any recommendations on app that will work with iOS for reading codes? If necessary I have old Android phone somewhere and I could certainly use that too if need be. Mostly I want to catch a code next time this happens so at least I have a clue where to look.
Also another thought, this could be an electrical pin just on the edge of contact? This issue seems to happen in cold weather and I have run into that issue a few times. Question is which electrical connector should I inspect? Mostly I would look for some corrosion on the contact or electrical pins, that has bitten me a few times in my years of fixing cars (one time my wife's Nissan Sentra would only start in the afternoon, never in the morning, turns out it was a fuel pump electrical relay that had some microcracks in the solder joints that would have good contact when it was warm but not when it was cold).
Read the thread- and specifically the post 37 in the link. I tried several apps on iphone SE and had no problems. Too many possibilities to guess. Need to scan for codes from all the systems- gotta have something to base a diagnostic direction on. Posted via the PriusChat mobile app.
