P0A08 error code

A 12-volt battery is needed to start the hybrid system.
After the sign “ready” lights up on the display, the hybrid converter supplies the car’s network with a voltage of 13-14 volts, which is used by the car’s systems and charges the 12-volt battery.
Is the "ready" light on on your car?

 

Another bit of info. I Googled how to check the charging system, and came across a whole series of YouTube videos created by Professor John Kelly with the Weber Auto YouTube Channel, part of the Weber University. This one in particular is very helpful and answered several of my questions.

The demonstration is using a 3rd generation Prius (2017), but the tests described would be similar for a 2nd generation (2004 to 2009).

I don't yet have a multimeter capable of checking DC amps, but I will investigate getting (or borrowing) one of those.

From the test just for battery voltage, I am definitely not getting any current to the 12V battery. Connecting my multimeter to the jump start contact under the hood and to ground, the meter reads about 12.5 volts whether the car is "OFF" or is "ON" and "READY".

Now I need to check the DC Amps entering or leaving the 12V battery to determine if the DC to DC Converter is working properly.

The only other possible cause I can think of would be if the fusible link block at the positive terminal of the 12V battery is blown. Checking the amps going to the fusible link block and then between the fusible link block and the battery positive terminal may be the test to determine what is wrong.

 

Thanks for your reply, which i just saw after posting another update. Yes, the "Ready" light comes on.

 

After turning on the "ready", check the output voltage from the converter white wire connector (B) pin 1.(AMD)
If there is a voltage of 13-14 volts on the converter, the wire to the fuse and relay box may fall off.

Converter by MAX2 posted Aug 21, 2024 at 8:33 AM

 

Thanks for the additional option in diagnosing the output of the DC to DC Converter. Am I correct that this larger white wire with grey connector (single contact grey connector pointed straight back and below other grey connector) is buried deep in the engine compartment, near the left and near the bottom of the inverter/converter? And, in order to get the connector off and measure directly at the converter, will definitely have to do some disassembly. Let me ponder that ... trying to find a used inverter/converter nearby in case that is required in order to fix, so if that looks promising, then disassembly will be necessary anyway.

 

Look at the diagram.
https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/21bpm/0a09265.pdf
The converter supplies voltage to the 12V system via the upper wire (AMD line). This voltage goes to the fuse and relay box.
The lower wire from the battery S (It is located on the positive terminal of the 12V battery, a small fuse and a white wire) goes to the converter. This is the feedback line. The converter reads the voltage directly from the battery via this wire and, if necessary, adds a voltage delta to charge the 12V battery.

 

A general update and some questions about Autel MaxiAP AP2500.

I reviewed the diagram that MAX2 shared. Found and downloaded the Toyota Service Manual for 2004-2009 Prius. Read the procedures for removing and installing the DC-DC Converter Inverter Assembly, should it come to that. Found the DTCs list and procedures for diagnosing each one, as well as other wiring diagrams.

The only error code that the Toyota dealer reported they found was P0A08. There are 11 possible trouble areas listed for that DTC. I have ruled out several, and several seem highly unlikely, but still want to be methodical and follow the procedure to rule out everything else before I remove and replace the DC-DC Converter Inverter Assembly.

So, to be sure I was following the correct DTC, I bought the Autel MaxiAP AP2500. Before connecting, I ensured that the 12V battery was fully charged (using external charger). The Autel found zero DTCs. I left the car on, drove it around the driveway a little, then turned on headlights and fan to run 12V battery down some. Eventually I got the same ABS, MIL, and other warning lights to come on. When I put it in Drive, the Red Triangle would appear. Repeated scans and still found zero DTCs. The 12V battery voltage is displayed, and is down to around 11V now.

Using a clamp on meter, no current flowing from the DC-DC Converter to the Unit A in the main fuse box under the hood. Using same clamp on meter at 12V battery, high current draw (over 40A DC) from 12V battery to run headlights, climate fan, rear defroster.

QUESTIONS:
1. Shouldn't some DTCs be found, with these warning lights and the obviously low voltage 12V battery?
2. Is the Autel MaxiAP AP2500 capable of finding and reading these error codes? Especially the P0A08?

 

Absolutely, yes.

It would appear not. Or, maybe it is not installed correctly.

 

Here are 3 pictures from yesterday's attempts at scanning for DTCs.

I'm pretty sure I installed the Autel correctly. I thought it would be capable of reading Hybrid Vehicle (HV) System related DTCs. Am I wrong?

 

That image just shows the engine PIDs. There should be another 10 - 13 ECU/systems that can be interrogated.

You may need to query the Autel website to find out the features your scanner has.

 

What app did you install?

 

Your picture looks like the app is only scanning for "generic OBD2". Did you go through a part of the setup where you select and download Toyota specific files?

That app is different than the MaxiAP200 that I am used to. When I look at the adcopy, it seems like the AP2500 has fewer functions than the AP200.

Posted via the PriusChat mobile app.

 

MaxiAP Diag, which was called for in the Quick Reference Guide.
During the registration process, I was prompted to download latest firmware, from 1.04.08 to 1.05

 

I am pretty sure I did select Toyota specific files, as every screen that came up I answered, including the vehicle make, model, etc.

I wondered about the differences between AP2500 and AP200 also, but I thought the AP2500 was an upgraded version of the AP200. Here is the Amazon link from which I purchased it:

https://www.amazon.com/dp/B0CWNKXDDS?ref=ppx_yo2ov_dt_b_fed_asin_title