brake abs vsc exclamation lights intermittantly come on

[Wagnerjp25]

I have a 2004 Prius. At about 50K miles several years ago the brake/abs/vsc/! lights came on on a hot day in stop and go traffic. Cleared when car cooled (after shutdown and restart). Then no problem for several years. Now with 100K it has started happening again. first time after a long downhill using B position on shifter, then after high speed freeway, then stop and go on exit. Seems to be heat related or after using engine braking for an extended period. Note that actual braking is NOT affected -- just the lights come on. Now that the weather has turned colder, it doesn't happen anymore. Any ideas?

[richard schumacher]

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.

[Wagnerjp25]

Originally Posted by richard schumacher

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.

Thanks for your reply. I checked like you said and I heard the whine. A little change in the situation though -- now I don't know if the problem is heat related -- it is happening in cool weather now (45-55 deg.) intermittently -- doesn't seem to be related to how I have been driving. The lights usually are out the next time I start the car -- but occasionally it takes two shutdowns and restarts over a period of time to clear the lights. I am afraid to take it to a dealer -- with an intermittant problem sometimes they just start replacing parts one by one to see if the problem gets fixed, and it ends up costing a lot of money.

[Patrick Wong]

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.