Driving home at night on the 405 freeway at approx. 65mph, suddenly all the dash warning lights illuminated, including the mil symbol, along with a warning symbol on the navigation screen. I pulled off the freeway and parked at the curb. After checking the owners manual, I slowly drove the rest of the way home on surface streets. The next morning (Monday) I drove my car to miller Toyota in culver city. The primary diagnosis was failure of the inverter coolant pump, which was replaced under the terms of my Toyota platinum extended warranty. However, upon further research, I discovered that Toyota had issued a technical service bulletin (tsb) covering this very part, on January 26, 2007, indicating that they were aware of this failure-prone part, and that an "improved" replacement assembly was now available to address the issue. In addition, replacement would be covered under their 5-year/60,000 mile Toyota powertrain warranty. Approximately one month later, on May 15, 2010, while driving my father's 2004 Prius to have new tires installed, the same sequence of events occurred. I immediately drove the vehicle to the nearest dealer, santa monica Toyota, where it was diagnosed with the same failure code, P0A93 (inverter cooling system performance). Although the vehicle had only 34,242 miles on it, it was not covered under the powertrain warranty, as the time limit of 60 months had expired. No amount of discussion with the dealer or Toyota's customer experience center could convince them that this part should be considered part of the hybrid system, and as such be covered under their 7-year/100,000 hybrid warranty (despite it being named the hybrid inverter coolant pump). On-line Prius-related chat rooms are full of identical situations involving this part. Clearly, Toyota knows this part is prone to premature failure, but continues to treat it as a "secret warranty" item in order to avoid having to issue a formal recall.

- Los Angeles, CA, USA

Failure of inverter coolant pump occurred without warning during normal driving conditions. This is apparently a common problem occurring at many different mileage intervals for other owners. Immediate significant loss of power and several warning lights illuminated. Cruise control and A/C went offline. Requires replacement which in this instance was $605.

- San Marcos, TX, USA

On 23 Jan 2010, while driving I-85N in the South Carolina mountains the car stalled at 70mph. An audible alert sounded, the car jerked and three warning lights went off. I coasted the car to the shoulder and shut the car down. I restarted the car -- the warning lights cleared -- and continued driving. About 30 minutes later, still in the mountains, the same things occurred (stall while driving 70mph on the interstate.) when I restarted the car a yellow "!" warning remained on. I continued the trip to Virginia with no further problems. The warning light went out. On 5 Feb 2010, while driving on I-95S in the South Carolina mountains the car stalled, warning lights and audible alarm sounded. Upon restart the "!" stayed on. This happened two more times; once on I-95 and once on I-20. The last two times the red triangle warning light stayed on also. On 6 Feb 2010, I took the car to Toyota center in columbia SC. The service manager told me the water pump needed to be replaced ($384) because air got into the system. I asked if that was why I could hear "sloshing" from the engine when driving; he said yes. I explained that I was confused since the coolant recovery tank never went below the low line. His response was that air in the system was a known problem for the Prius and that I should keep the coolant level higher than marked. Also that driving in the South Carolina mountains -- both the heat of the engine and the angle of ascent and descent -- is probably what triggered the problem. Prior to both trips, the car was checked by a mechanic. Fluid levels were clear and adequate. I am now in the flatlands of Texas, and I can once again hear the sloshing sound coming from my engine. Beyond the expense I am concerned that the engine is completely stalling. If this were to occur in rush hour in a crowded city I'm not sure the car would be safely navigable to the shoulder.

- Seguin, TX, USA

This happened to me and cost over $700 to fix: Failure of inverter/converter coolant pump. Hybrid vehicle has 2nd coolant loop for high voltage inverter/converter. Failure of inverter/converter coolant pump allows inverter coolant temperature to rise well above nominal. At a certain trigger point hybrid control ECU sets a trouble code that immediately disengages operation of inverter/converter (and simultaneously disengages cruise control and A/C, which runs of alternating current produced by inverter). Immediate impact is a sudden loss of vehicle drive power as inverter/converter supplies to electricity to motor generator 2 (MG2) which is directly connected to drive wheels and supplies needed motive force to maintain highway speeds (ice alone is insufficient). Also inverter/converter coolant loop provides cooling for MG2 & MG1. Continued operation of vehicle with failed inverter/converter coolant pump could result in catastrophic failure of main electric drive MG2 and subsequent loss of motive power. Pump failure occurs without warning, although there may be a brief period of intermittent pump operation/non-operation prior to final failure. The failure seems to be the result of either a defective inverter/converter pump ass'Y or one insufficiently engineered to withstand continuous operation in such a critical component. Pump failure occurred after approximately 160,000 miles, although has been known to occur in other instances as early as 32,000 miles. Sudden loss of power and disengagement of cruise control at interstate highway speeds could cause driver to lose control or to be unable to safely steer to a safe breakdown lane.

- Austin, TX, USA

Failure of inverter/converter coolant pump. Hybrid vehicle has 2nd coolant loop for high voltage inverter/converter. Failure of inverter/converter coolant pump allows inverter coolant temperature to rise well above nominal. At a certain trigger point hybrid control ECU sets a trouble code that immediately disengages operation of inverter/converter (and simultaneously disengages cruise control and A/C, which runs of alternating current produced by inverter). Immediate impact is a sudden loss of vehicle drive power as inverter/converter supplies to electricity to motor generator 2 (MG2) which is directly connected to drive wheels and supplies needed motive force to maintain highway speeds (ice alone is insufficient). Also inverter/converter coolant loop provides cooling for MG2 & MG1. Continued operation of vehicle with failed inverter/converter coolant pump could result in catastrophic failure of main electric drive MG2 and subsequent loss of motive power. Pump failure occurs without warning, although there may be a brief period of intermittent pump operation/non-operation prior to final failure. The failure seems to be the result of either a defective inverter/converter pump ass'Y or one insufficiently engineered to withstand continuous operation in such a critical component. Pump failure occurred after approximately 160,000 miles, although has been known to occur in other instances as early as 32,000 miles. Sudden loss of power and disengagement of cruise control at interstate highway speeds could cause driver to lose control or to be unable to safely steer to a safe breakdown lane.

- Dahlgren, IL, USA