What does this mean?

[ron69424]

Driving home today the red triangle, amber brake symbol, vsc light and maint req. lights came on. The car seems to run normally and all the fluids are full. Our Toyota dealer said to bring it in for a $100 diagnostic tomorrow morning. Any of you prius gurus know what all these lights mean? Any advise will be greatly appreciated.

[Patrick Wong]

I'm assuming that you have a 2G. During summer season, a common problem is that the inverter coolant pump fails. This causes the inverter to overheat and the DC to DC converter will allow the voltage on the 12V bus to drop. The low voltage causes the brake and VSC lights to come on.

If your air conditioner does not blow cold air, this is another symptom supporting the likelihood that this is the problem, since the inverter powering the air conditioner compressor will shut down.

One way to assess whether the inverter coolant pump is running is to look at the fluid level in the container when the car is either IG-ON or READY. You should be able to see a step in the fluid where the rear is higher. Also, when the engine is off you should be able to hear the pump running; it is located near the driver's side headlamp assembly.

If the pump is OK, then another possibility is that the brake system has a problem.

Regarding the MAINT REQD light, this is just based upon a 5K mile counter, so perhaps your time has come to change engine oil?

It is normal for the dealer to quote a diagnostic fee to ensure you are serious that a problem is present; if the issue is covered under warranty then that fee should be waived.

[ron69424]

Thanks Patrick. Yes it is a 2004 Prius. I drove the car again. The amber brake light , vsc lights went out temporarily and then came back on. The red triangle and check engine (not maint req) lights stayed on the whole time. Also the air conditioning stopped cooling during the drive. Is the inverter coolant pump under the hybrid warranty (100.000 mile)? Would you recommend anyone to try to change this out themselves?
Thanks for your help.

[Patrick Wong]

Hi Ron,

If the inverter coolant pump is the problem, it is covered under the powertrain warranty of 5 years/60K miles. See the attached TSB for more info.

Regarding trying to replace the pump yourself, this would be a moderate difficulty DIY project. The main challenge would be draining and replacing the inverter coolant so that no air is left in the system. If you decide to take this on, I urge you to download the relevant repair manual pages at techinfo.toyota.com

Good luck.

[ron69424]

Thanks again Patrick:
My '04 has more than 90k miles so the warranty is long gone for the inverter pump. I found a local dealer that sold me one for $110. Another dealer quoted me a price of $745 for the complete package installed. I'm not made of money so I got the instructions and replaced the pump myself today as well as the engine coolant. The bleed valve makes the job of removing the air quite doable. Getting the air out of the engine cooling system took more time than the inverter pump. It requires a 6mm allen wrench to bleed the radiator.

The inverter pump works well and is quieter than the old pump. However the red triangle and check engine light remain illuminated. Is there something required to reset the system? I hate to pay Toyota a diagnostic fee just to turn the lights off.

Thanks for your help. You have saved me MEgga bucks!

[Patrick Wong]

Hi Ron,

Try disconnecting the negative terminal of the 12V battery for 10 minutes, then reconnect. It may be easier to remove the negative cable where it connects to the vehicle body.

If the warning lights remain on, then you will need a code reader that can retrieve the DTC and reset the ECUs.

[ron69424]

Hey Patrick:

Disconnecting the neg. battery terminal did the trick. Our car is back to normal again. Thanks for your help. Ron

[Patrick Wong]

Hi Ron,

Congratulations on saving ~$600 in exchange for a few hours of work! That sounds like a great tradeoff to me.

I assume that you drained and replaced the inverter coolant as well as the engine coolant? Regarding the engine coolant, did you open all three drain cocks (engine, radiator, and coolant heat recovery canister)?

I hope you used the pink Toyota SLLC when replenishing the coolant. How many gallons did you use: my guess is that 3 gallons were required?

[ron69424]

Hi Patrick:

Yes, I figured while I had the car up on jacks I might as well drain and fill both coolant loops. Yes I did drain all three drain cocks. The canister drained about 90% with just a little out of the radiator and block. I used about 1.5 gal. of Toyota's SLLC non diluted coolant. The refilling of the engine coolant took the most time and patience. I really don't know if the radiator bleed did anything at all even though I tried using it.

I guess the only thing left is to replace the brake fluid. I understand that may be a dealer job.

Thanks again for your knowledge and advice. Ron

[Patrick Wong]

Originally Posted by ron69424

...I guess the only thing left is to replace the brake fluid. I understand that may be a dealer job...

Hi Ron,

Thanks for the detail on your coolant drain and replace. I didn't know it was possible to buy full-strength SLLC. I had a similar experience as you with respect to the canister drain passing most of the fluid that came out of the engine coolant loop.

Well, I flushed the brake fluid on my 2001 a couple of years ago. My procedure was to first suck out most of the old fluid in the reservoir using a rubber squeeze bulb. Then I filled the reservoir with fresh Toyota DOT 3 brake fluid.

I had my wife very gently depress the brake pedal and hold it slightly depressed while the car was IG-ON (so that the brake system would be powered up.) Starting with the rear wheels and then moving up to the front, I slightly opened up one drain cock at a time. That resulted in a large flow of brake fluid out of the drain cock, through a clear vinyl tube, into a glass jar. The old fluid was not that dark, unlike old fluid from normal cars, so it was hard to tell exactly when the old fluid was exhausted and the new fluid began. Then I closed the drain cock and had her release the pedal. I replenished the fluid in the reservoir and moved to the next wheel, and repeated until all four wheels were done.

The main concern is to ensure that no air gets into the system upstream from the brake wheel cylinders; for example, allowing the brake fluid reservoir to run out. If that happens, a dealer visit will be required to have the brake lines properly bled. I used two bottles of brake fluid and decided that was sufficient to declare victory.

One disadvantage of my method is that the new brake fluid may not flow through all portions of the brake actuator assembly. However, a big advantage is the relative low cost of my method.

The 2G brake system is more complex than Classic and I haven't tried this procedure on my 2004 yet. When the car has logged more miles I plan to try it out, after studying the repair manual to see whether modifications are required to the procedure.

Worst case, the procedure doesn't work, air enters the system, and I have to tow the car 5 miles to my local dealer for help. This would not be the end of the world, should that happen...