brake abs vsc exclamation lights intermittantly come on

Are you in northern California, a cool climate?

I saw that when the inverter coolant pump failed. With the car in IG-ON you should hear a continuous faint whine from the front left of the drive compartment and see turbulence in the inverter coolant tank. If not, bingo.

 

Prius makes several noises. The inverter makes a whine. The inverter water pump sounds like an aquarium pump and is located behind the driver's side headlight assembly.

My guess is that this pump has failed, but this does not become apparent when the ambient temp is low or you are driving short trips.

 

Patrick, Sorry to jump in an old thread but I'm curious about your statements above. I have the exact same problem here. When my 2008 Prius (with 110k miles) is cold, the four warning lights (!+ABS+VSC+brake) are not present AND the inverter pump appears to be working fine. I hear it and I see turbulence in the reservoir. The inverter pump was replaced 4 years ago and I see the replacement pump has a black base making me think it was not the revised pump (that has a silver base). My 12v battery has been replaced once by me with an OEM battery (maybe two or three years ago at most). Connections are all solid including ground to chassis. Battery seems to be within spec. Using the MFD, I get 12.1v after sitting overnight, 11.4v with headlights/rear defrost on and 13.9v when car is on. Based on your statement in this post, it sounds like it is possible that the inverter pump could be failing intermittently i.e. when hot. Is this true? And perhaps I need to check the pump for turbulence right when I get the warning lights. The only other anomaly is the slip control light has tripped very briefly while driving down a perfectly smooth road and the "brake" triggered very briefly. It's the same sensation as you have when the car is really losing traction i.e. accelerating from a stop in rain.....like a tap on the brakes, not enough to slow me down but still unnerving. It's like a false trigger is setting off the slip control. Could that be due to inverter intermittent failure as well? I've got a Mini VCI Cable on the way. I'll pull the codes when I get it. Any help is appreciated. Thank you for all of your posts. They've been real helpful.

 

actually, your 12 volt is not within 'spec'.

 

Yes, that is an excellent idea. Also check battery voltage (use a digital multimeter) when the Prius is READY and the warning lights are on.

I agree that the 12V battery voltage is on the low side, try putting a charger on the battery overnight to see if that helps.

Maybe. Did this happen on dry pavement? What is the tread depth of your tires, and have you checked the tire inflation pressure?

 

Thanks for the replies. Tires are less than a year old and pressure is 5 lbs over stock. With regard to charging, I understand that I need an AGM charger. I searched briefly for one. Any suggestions? Another note, mileage has been a bit off for a few months i.e. getting 47 when I used to get 50-ish. Thought it might be winter plus new tires (non energy saver this time). Maybe the battery has been "going south" for a few months. Seemed like I just put the battery in a couple of years ago at the most....so battery issues seemed unlikely....ugh! Anyhow, I read the battery voltage this morning and just now (a few hours later) with a DVM. I measured at the jump terminals under the hood. This morning I got 12.5 initially (with the car totally off). I turned on the headlights for just a second (to get rid of the extra charge that I've read about giving false readings) and got 12.4. Checked a second time with headlights on and got 12.1 volts. I checked just now (several hours later) and I got 12.6 under the hood with no lights turned on. Flashed the headlights for a second and got 12.5. Turned headlights on and left on and got 12.05. I've got the DVM in my car. I'll check voltage next time the warning lights come on. Note that my voltage readings in my first post were made from the MFD, not my DVM. Feel free to comment on anything I've stated. Thanks for the help!

 

Took a drive this morning and all four warning lights came on again after 10 minutes of driving. Interesting thing is the skid control light flashed (and briefly activated the brakes) almost immediately before the four warning lights came on. I pulled over and checked voltage without turning off car. Voltage was 13.8 with DVM. Turned car off and read 12.6 volt. Went to the store and bought an automatic battery charger (Schumacher XCS15W). Pulled battery out of car and battery charger (tester function) indicated battery was at 12.9 at initial reading. Set it to AGM battery type and a 3 amp charge rate and it was at 100% within 30 minutes and the charger put itself into "charged/maintain" mode. Voltage stayed at a constant 13.1 volts after charging (checked with battery charger tester and DVM). I think something else is going on and the battery is ok. I don't even think the battery is 2 years old. I put the battery back in the car and it read 12.5 on the MFD followed by 12.3 in ready mode. Any thoughts? I'll pull the Prius specific codes after I get my mini VCI cable which should arrive on Tuesday.

 

Hence, the DC/DC converter was still operational at the time this voltage reading was taken. Did you have an opportunity to check the inverter coolant reservoir for fluid turbulence at that point? The inverter coolant pump probably is running OK.

I agree. The next step is to retrieve the logged DTC with Mini VCI.

 

Doh! I spaced on checking the pump. So I just went out and drove same route and got warnings lights in nearly the same location. This time I stopped and checked inverter pump and reservoir. Pump was working and turbulence was seen in reservoir. I think pump and battery are ok. I'll check codes on Tuesday and post them. I read in another post that the brake stop switch could also cause similar symptoms. I just hope its not some expensive ECU.

 

Logged code was C0210 which translates to rear speed sensor RH. I'm going to bet that the problem is the rear wheel bearing hubs that I replaced 2 years and 3 months ago. They were the cheap ones from 1AAuto ($80/pair) that included the hub and sensor.
2008 Toyota Prius Rear Wheel Bearing & Hub Assembly Pair at 1A Auto.com
I checked the sensor wiring and connections and everything looks ok. I jacked up the car and the driver's side rear wheel doesn't turn too well (emergency brake off)....and not as well as passenger side. Maybe there is supposed to be a little drag on the rears with the transmission in "park". And I don't hear any wheel bearing hum so I think the drag is the brakes. Anyways, I'd guess the sensor in one of the cheap hubs is starting to crap out. I think the warranty on the hubs was 2 years. Ha! Hubs were and still are 1/3 the price of Timkens. They're easily replaced. Maybe I should throw another set on. Thoughts?

 

Any thoughts on the logged code? Any help is appreciated. Thanks.

 

Yes, I would replace the sensor if you do not see any problem with the wiring.

The rear axle has no connection with the transaxle and therefore it doesn't matter if the transaxle shift position is in P or any other position. The rear wheels should freely spin when the parking brake is released. Since the left rear wheel is binding, that should be checked out. If the brake is always dragging, that will heat up the wheel hub and maybe the sensor prematurely failed due to the excess heat.

 

Great news! I replaced the rear wheel bearing hubs last night and lights have not come back on. So I think the fix was indeed a new set of rear speed sensors (which are included with new rear wheel bearing hubs). I managed to avoid a dealer visit on this one. I spent $25 on the mini VCI cable w/ techstream and $76 on the new hubs. Not too bad! The dealer wanted about $1100 to replace the rear wheel bearings when I inquired over 2 years ago. So glad I did the work myself. Wondering if I should clear out old codes?

 

Yes.

You had earlier reported that the LR wheel was binding. Now that the hub was replaced, does it turn freely?

 

Honestly, I was in a hurry and did not check for binding on rotation of either wheel. I do know that the brake drums came straight off with no issues whatsoever so that leads me to believe there were no dragging shoes. Brake shoes and drums looked fine. May have been the cheap bearings starting to wear out. I had 2 years and 3 months on them. Original bearings lasted just under 5 years. I'll check out the wheels over the weekend and follow up. Thanks.

 

Both wheels have some drag in one spot. Spot seems to be about 25% around the circumference of wheel. I assume a shoes are dragging. Parking brake was off. I've never touched the brakes on this car other than pulling the drums off for the wheel bearing replacement.