Intermittent Hybrid System Problems

I have a 2005 Toyota Prius that suddenly began displaying several error messages after the air conditioning system had been repaired and the Coolant Heat Storage Water Pump System (R & R Water Pump Assembly w/Motor & Bracket) had been replaced. The car operated with no problems prior to these repairs, and I hope that someone on this Forum can tell me what may be causing these issues.

While driving the Prius for about 15 minutes with the air conditioning running at maximum, the Multi-Information Display suddenly illuminated the Hybrid System Warning Light (red car with exclamation point in the middle). The Instrument Cluster immediately lit the Master Warning LightMalfunction Indicator Lamp (yellow engine check light). A few minutes later, the Brake System Warning Light (yellow bracketed circle with exclamation point in the center) began to glow which led the air conditioning system to suddenly not blow cold air. I did notice that the air conditioner did not consistently blow cool air prior to all these warning lights coming on (sometimes, this air would be ambient temperature or a bit warm). Obviously, I took the car back to the Toyota Dealership for further diagnosis. They cleared the errors, but the lights reappeared as mentioned above. After a few days of trial, the Dealership is still investigating.

Has anyone even come close to seeing these issues on their car? My Prius only has 26K, and has been well cared for. I'm hoping this could only be a loose connection caused by the above repairs. Anyway, thanks in advance for your feedback on this post.

 

Thanks for the information thus far. To further elaborate on what had been repaired on the Prius, the body shop removed the radiator to further align the metal sidings as well as replace the AC Compressor. The Inverter Coolant Pump also had a slow leak, which prompted them to replace that as well. The error messages began appearing a few minutes after I drove away from the body shop.

It seems that (based on my research thus far) air pockets within the Inverter Coolant System may be causing the Inverter to overheat and issue the error codes before shutting down. I visited the Dealership first thing Monday morning to discuss my investigations and look at the car. When we viewed the Inverter Coolant Reservoir, the fluid definitely was lower than the low limit line. The electric pump also failed to start when required. We left the reservoir cap off the reservoir in preparation for the tech to fill the bottle, but when I came back about an hour later the reservoir was empty and pink coolant could be seen underneath the car.

Needless to say, there is an obvious leak in the Inverter Coolant System. I wonder if they tightened every hose connection? Interesting turn of events, and I definitely will keep everyone informed.

 

I gave the Dealership the repair order from the body shop to help them with their investigations, but I believe the only thing the body shop did was remove the radiator to further straighten its side supports due to a previous mishap. The air conditioning system also needed repair since it did not consistently blow cold air into the cabin (I live in Texas). Had I known I would have these problems AFTER a repair, I would have left the car the way it was since I had no trouble with the Prius up to that point. Nevertheless, the Dealership and I now have to determine what could be causing the leak of the Inverter Coolant System.

I admit I'm astonished as to why the Dealership would take so long to find a leak, since a leaky connection visually stands out like a dripping faucet. I would guess this leak may be located around the hoses connecting the radiator (which the body shop removed) and / or the Inverter Pump (which the Dealership replaced). Anyway, I'll post more information as I obtain it.

As for error codes, the only thing I can muster from the paper the Dealership gave me is Code 200 (which had been circled). I have not asked them a complete code listing since I want to keep the Dealership on my good side (it seems they won't charge me for their investigations, but we shall see).

 

Here's an update as of 23Jul2008. I've taken the car to two Toyota Dealerships and two independent shops thus far, had the Inverter Pump replaced and its coolant system filled and purged of air, but the above error lights appear again!!! It seems to be a heat-related issue since the codes show up after driving the car on surface roads for about 10 minutes (the car runs well on the freeway). In the morning, the car starts with no error lights whatsoever but eventually turn on after the engine compartment warms up with the hood closed.

I'm going to visually check around the engine compartment tomorrow to determine if there is a stray sensor or any kinked hoses. If all seems well, I'll have to take the Prius back to the dealership for further diagnosis. I'll also continue my online investigations on how the Prius Inverter operates. Can anyone tell me how the Inverter System senses an overheated condition? Where are the sensors located? What about radiator / condenser temperature sensors? What is the overtemp setpoint of the Inverter System? Any other information would certainly be appreciated.

 

Interesting information! I also read a post where the radiator fan had been installed reversed and caused overheating. The radiator fan operates on my Prius, but I'll have to check in the morning which way the air flows.

Can you elaborate on the two fan motors of the radiator, their orientation, and the minimum air flow required through each fan? Is there a way to adjust the position of the fan assembly on the radiator housing for better air flow? I didn't realize the Prius has a two-fan radiator design, but then again I have not completely remove the front engine molding to notice a second fan (I only saw one through the molding crevices).

 

Thanks for everyone who helped me on this problem.

After going through nearly two weeks of constant errors reappearing with no end in sight, despite taking the Prius to so-called "experts" (two Toyota Dealerships and two independent shops), I decided to do my own visual inspection of my car. The problems seem to be caused by a loose radiator fan blade (the seven-blade one, where the blade mechanism had slipped off the motor shank) and a leaking HV Inverter Coolant Reservoir at the Inverter junction itself (fluid drips slowly with the cap removed). Since the fan had jostled loose, I could not determine whether it provided proper airflow direction. Needless to say, I took my Prius back to the original body shop and pointed these issues to them. They will fix at no charge, since they provide a lifetime warrantee on their repairs, and hopefully this will be the end of this fiasco.

 

Well, this saga continues! After the shop fixed the radiator fan (also verifying air flow for both) and the leak in the HV Coolant System, these error messages still come on. I had the AC running prior to the codes returning, which leads me to believe that the shop may have used the wrong type oil after they replaced the AC Compressor. I'll take the car (AGAIN) to a Toyota Dealership for them to diagnose.

While I continue my investigations, can someone tell me how a shop determines whether the wrong type oil had been used? If the wrong oil had been used, what would the procedure be in completely purging the AC line of the old oil in preparation for adding the correct one? Would any other AC parts need to be replaced?

 

Well, my car finally has been fixed! Aside from the earlier-mentioned parts that needed to be replaced, the latest Toyota Dealership I took my car in found a leaky o-ring within the HV Coolant Reservoir and a malfunctioning Radiator Water Pump (P/N G9020-47031). After replacing the two pumps, inverter reservoir, and various o-rings, the car now runs like a champ.

I'm glad the Inverter Coolant System now operates with no problems as the temps in Texas these days have surpassed 100°F. Thanks everyone for your help.