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Discussion Starter · #1 ·
On two occasions in the past month I've experienced the Master Warning Light, amongst other warning light icons, coming on. Both times it occured when the outside temperature has been 90+ degrees with high humidity. My Prius is an '05. Anyone else experiencing this problem or what it will take to 'fix' the problem?
 

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Discussion Starter · #3 ·
On both occasions the Master warning light came on after driving the vehicle between 30-50 miles and while pulling into parking lots. I don't know if the high outside temperature and humidity have anything to do with the problem but it just seems coincidental.

Following the first occurance, I had the vehicle towed to the local dealer. They supposedly fixed the problem by indicating that there was a loose cable. I am currently waiting for another dealer to call me regarding their diagnosis of the problem.

Once the master warning light comes on and the vehicle is shut off, you can start the vehicle back up but cannot put it into Drive or Reverse; Neutral is all that can be done.
 

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The master warning light is too general to give you any direction. That's like saying 'my car won't start, what's wrong?'

The other indicators, short of getting the diagnostic codes, would probably give a better idea as to what might be going on. Especially what you find in the MFD.

Outdoor temp alone should not matter. The only way I think it would matter (but shouldn't) is if the battery is overheating or thinks it is overheating in which case its fan will go on loud.
 

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We just had a similar problem with our 2004 Prius a couple of hours ago, which would be about 6:30 am July 22, 2006. Temperature about 75, relative humidity very very high. Car was in driveway overnight. Based on a quick web search, I saw that a common reason for the light was multiple misfires. I checked the air filter, and there were some leaf fragments on the dirty side. I vacuumed the filter carefully. Re-installed filter, started the car, and immediately stepped on the accelerator while in Park to hopefully get the engine up to speed and out of a low-speed mis-fire range. The light did not come back on. I drove the car a few miles and still no warning light.
Conclusion: Really can't draw much of a conclusion, this might be a coincidence, but these are two things you can do without a tool kit or repair manual and they only take a few minutes. Caution: Be careful to clean off the air filter cover before you take it off. You don't want to drop any sand into the nice engine.
 

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That's possible. Again though, codes should have come up. Timing is critical with this system, so even one miss should have been detected and if serious enough to be noticed, flagged.
 

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Discussion Starter · #14 ·
I don't understand what they mean but here are notes from the copy of the paperwork I received:

CCS-POAA6

Gateway: B1200 Body ECV comm. stop
B1207 Smart key ECV comm. stop
B1271 Combination meter ECV comm. stop

HCECV - POAA6
Hybrid Battery voltage system isolation fault

C - High impedance short in HV Transaxle

R - Pushed vehicle into shop and checked codes. Found POAA6 with Info 526/613 codes - replace transaxle
 

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I never would have figured on that. The 2004 repair manual doesn't have P0AA6 (though it does have P0AA5) but it did have P3009 with INF 526, which basically says the high voltage system is all screwed up (short to body ground) but can come from anywhere.

High Voltage Power
Short Circuit
526
Insulation resistance of high
voltage circuit and body is
low
 Frame wire
 System main relay
 System main resistor
 HV battery assembly
 w/ motor compressor assembly
 Battery ECU
 HV transaxle assembly
 w/ converter inverter assembly
 Main battery cable
 Main battery cable No. 2
 Battery plug
 Frame wire No. 2
 Junction block assembly
 

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Rick Prill said:
I don't understand what they mean but here are notes from the copy of the paperwork I received:

CCS-POAA6

Gateway: B1200 Body ECV comm. stop
B1207 Smart key ECV comm. stop
B1271 Combination meter ECV comm. stop

HCECV - POAA6
Hybrid Battery voltage system isolation fault

C - High impedance short in HV Transaxle

R - Pushed vehicle into shop and checked codes. Found POAA6 with Info 526/613 codes - replace transaxle
Nasty one. The HV system (as you probably already know) "floats" and is isolated from the chassis ground. If the HV system is leaking current to the chassis, the system is designed to close the HV battery relays to prevent a potentially hazardous situation from occuring.

Interesting how localized and specific the codes were.
 

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i had this problem with my 01 , may be irrelevant, but it happened when temperature was above 90 degrees, and the inverter/converter overheated due to a airpocket which decided to disappear on that day, i luckily filled it up and i was good to go.
 
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