P0A08 error code

I suggest that you inspect the inverter coolant pump yourself, to verify that it is working. This is easy enough to do:

1. Make the car IG-ON (from IG-OFF, press the POWER button 2x without depressing the brake pedal.) All of the instrument panel warning lights will be on.

2. Open the hood and look for the inverter coolant pump behind the driver's side headlamp. Listen for the sound of the pump running (should sound like an aquarium pump and you should not hear air bubbles.)

3. Look at the inverter coolant reservoir and note turbulence in the fluid which shows the fluid is circulating.

Also note that the original 12V battery passed the "load test". This is why I suggest that owners not bother to pay for this test at the dealer, if there are any questions about the battery just replace it.

 

The yellow is the brake fluid. Inverter is the pink. See pic. 103 in this post:
http://priuschat.com/forums/gen-ii-...-visual-inspection-dummies-2.html#post1118652

 

Your car and city caught my eye.

I just bought a 2006 Prius and I live in Aptos too. I get back there in mid may. Perhaps we can exchange some info?
gabe

 

Question for the original poster or anyone else who has had the P0A08 code. Did you also get a high pitched alarm tone?
TomK

 

Hi Kutch, this is a 14 year old thread so the original poster might not be around! but to answer your question YES! i get the high pitched alarm tone along with P0A08 (and others) randomly every few months, im not 100% sure but think the alarm is part of the brake master warning once the aux battery gets down to about 10 or 11v the brake system has a hissy.

Matt

 

Very interesting ozmatt, in my searching I have found very few people mention the high pitched alarm tone. Mine has not happened again since that first time and I have done nothing except some prodding and pocking around. Seems strange that Toyota would put that system of alerting the driver of something like that and it turn out to be what seems like most times as nothing more than a hiccup.
TomK

 

Hi Kutcht1

I guess it's to make you immediately aware that something is very wrong! and potentially dangerous.

One of our cars was doing this every once in a while and it went on like this for a couple of years believe it or not, turned out the 12v aux battery was actually the cause all along and it hung in nearly dead for years getting worse and more frequent towards the end of its time.

..Never trust the 12v aux battery in a Prius because they need so little power to READY detecting a weak aux battery can be very difficult

Matt

Posted via the PriusChat mobile app.

 

Thanks again for the response Matt. I will keep a close eye on the 12v this summer and will for sure check things closer to winter! It has not done this since and voltage stays well above 12 volt but battery is over 5 years old now.
TomK

 

Hello! I am hoping even though this an older thread, someone will be able to assist me.

Our 2004 Prius recently had the BRAKE, ABS, RED TRIANGLE, warning buzzer go off while my wife was just backing out of the carport, so she used another car for her errand instead. A few days later it seems to start and run OK, so I drove a short distance until same symptoms appeared. First had it towed to a repair shop (that had replaced ABS 18 months earlier) and they said it was not an ABS issue, but a low voltage issue. I replaced the 30 month old 12V auxiliary battery and still had low voltage codes, but not as many. From there had it towed to dealership. After 2 days they said after charging the new 12 volt battery, it checked out fine.

Now, a month later, same problem and warning lights.

After new battery was installed, I ran the auxiliary battery tests by accessing the diagnostic tools using the multi-function display, and all voltages of the 12 V battery seemed within range (static test, under load, and while charging).

Now the tests show about 11.5 volts or less, even when charging.

I checked the inverter/converter coolant pump as described in earlier post, and could only hear a slight hum and feel a slight vibration. Could see no "gurgling" at the coolant reservoir.

Is it likely the inverter/converter is no longer doing its job? Anything else it could be?

 

If you want help, you need to post the trouble codes that are causing the warning light to turn on. Everyone will just be guessing what your car's problem is until you post the trouble codes.

 

Thank you. The dealer report showed error code P0A08 at the time they had car a month ago. See attached copy of report. I'd be willing to invest in a scanner, if I could find one best suited. My knowledge of scanner types, brands, and terminology is pretty limited. Open to any suggestions or recommendations. Does the inverter water pump sound like a possible cause, based on my recent inspection of no turbulence in reservoir?

 

check inside the inverter coolant reservoir for fluid motion with the car 'on'.
it could be that the inverter is not working properly. they are cheap enough salvage if it needs to be replaced.
it will take more testing to determine the problem. you may need a prius aware scanner, not sure what your shop is using.
see post #2:

p0a08-dealer-clueless.151186

 

Thanks. I checked the inverter coolant reservoir for fluid motion while the car was "IG-ON (from IG-OFF, press the POWER button 2x without depressing the brake pedal.)" per second post in this thread. Is this what you meant, or should car be turned on and in "Ready" mode?
And I checked out the post you linked. I have seen other posts about the Mini CVI being recommended. Is this just the connector for the OBD port, or is it the complete scanner? Any additional info on what would be a good Prius aware scanner would be appreciated. Do not know what type of scanner the dealer used, but I would hope an appropriate one.

 

Yes, that is what was meant. The result was? Running or not?

Mini VCI is just the cable, but they mostly come with a copy of Techstream.

Nowadays, a good bang for your buck is the Autel AP200. This thread reviews several scanners and leans toward the Autel AP200 for the casual user.

A genuine Toyota dealer will use Techstream which is the gold-standard Toyota scanner.

 

dolj,

Thanks for the answers and pointing me to the other thread with so much about Gen2 OBD2 apps. mr_guy_mann's Cliff Notes version post with his summary (and the posts following it) were just what I needed to become intelligent enough to ask a few questions. I am beginning to think this may be beyond my skill level, but we'll see.

And, in answer to your first question, I could hear the pump making a very small amount of sound (more of a hum), and I could feel slight vibration when I put my hand on the pump and the coolant hose connected to it. I could NOT detect any fluid motion in the reservoir itself, even with the cap removed. Perhaps I need to repeat the test and look more closely.

 

ig on is all you need. if you make it ready, wait until the engine shuts down so it isn't creating vibrations in the fluid.
it's possible that the pump is humming but the impeller is shot

 

Thanks for the clarifications. I have done some more testing (charged auxiliary battery and double checked inverter coolant pump), and here are my results:

I disconnected the negative cable from the battery (where it connects to car body) prior to charging (per instructions I found in Owner's Manual)
Prior to charging battery, voltage read 11.70 (at battery terminals, with volt meter)
When charging started, digital display on charger read 11.6
Charged for 6 hours (until it got dark and I didn't want to leave it unattended overnight.) Digital display on charger read 13.6 when charging paused.
With volt meter, voltage at battery terminals measured 13.02
Next morning, prior to resuming charging, voltage at battery terminals measured 12.79
When charging resumed, digital display on charger read 13.9
Within 10 minutes, digital display on charger rose to 14.9, then dropped to 13.2
Digital display at charger slowly rose again to 14.4, before dropping again to 13.6 about 1 hour later.
Over next three hours, digital display at charger rose to 14.7, and within an hour after that had dropped to 13.6

This is the first battery charger that I have owned (and first time using a charger), and after re-reading the instructions, it is possible that the charger had gone into Auto Maintenance Mode. This may account for the digital display on the charger rising and falling so many times. The battery charging status symbol on the charger has 5 "segments" that will show solid segment(s) when a certain degree of charging is complete, and the next segment above that flashes to indicate charging is in progress. The most I ever saw solid were 4 of the 5 segments, with the 5th segment flashing. There is a also a "Bad Battery" symbol which illuminates if the charger determines the battery is "Bad". This symbol never illuminated.

I disconnected charger after being connected for 5 hours (plus 6 hours the night before) for total charging of 11 hours.
Voltage at battery terminals using volt meter read 13.33
6 hours later, voltage at battery terminal measured as 13.07
The next morning (another 12 hours later) voltage measured 13.00. This is 18 hours after charging discontinued. Negative battery cable was still disconnected, so no possible load or drain on battery.
Re-connected negative battery cable. Voltage measured 12.81

Started car and let it run for a minute or two.
With car still "ON" and "READY", measured voltage at battery terminals with volt meter. Voltage read 13.85. Does this indicate battery was being charged?

I turned car "OFF", and then started in "ON" mode only, to see the battery self-check readings:

First reading: 12.7 (with IGN "OFF") It is my understanding that reading should be between 12.4 to 12.8 volts for a good auxiliary battery.





Second reading (under "load", in "ACC" mode): 12.4 (with IGN "ON") It is my understanding this puts battery under a "Load", and should read 12.0 V (+) and hold steady.





Third reading (after pushing Power button with foot on brake one more time to make system "READY"): 12.2 From my understanding, this third value SHOULD BE between 13.6 and 14.4 V to indicate that the charging system is working correctly.





After performing the three self-diagnosis checks, I re-checked voltage with volt meter at battery terminals: 12.34

Next, I performed a check of the inverter coolant pump, by putting car in IG-ON mode by pressing power button twice without depressing brake pedal. I could hear slight hum, felt vibration at each end of coolant hose, and could see some slight movement in the coolant in the reservoir. Of all of the supported video formats, Dropbox is not included, so can't attach video directly. Here is a link to a very short video showing movement in the coolant. Anyone using this link should be able to view without having to be a member of, or join, Dropbox (but you may still get asked or prompted to do so. Just ignore and continue) Dropbox

After checking the inverter coolant pump, I again checked voltage at battery: 12.63

I will be checking voltage at auxiliary battery later today, so updates may follow. In the meantime, do these findings point to most likely problem?

 

Some updates.

The 12V battery seems to be holding a charge well. The slight drops in voltage I am seeing may be due to the DC/DC inverter/converter not working properly for the short distances I have driven.

I drove 5 miles this morning, with the on-screen Diagnostic Check / Vehicle Signal Screen up on the center display (same screen as shown in picture of "Third Reading" above). Instead of showing the 13.6V to 14.1V as expected, it showed 11.6V to 11.9V the entire time.

1. Does this confirm that 12V battery is not being charged properly? Is the DC/DC inverter/converter not working properly?
2. Is the amount of "motion" of the coolant in the inverter pump reservoir indicate that the inverter coolant pump is working properly?
3. If the inverter coolant pump is not working properly, would that cause the DC/DC inverter/converter to not work properly (by overheating) and therefore "shut down" to protect itself and not charge the 12V auxiliary as it should?