P0A08 error code

Well, a final update.

I worked my way through the Toyota 20 step Inspection Procedure for diagnosing the P0A08 DTC and the DC-DC Inverter Converter was proven to be the problem. The Inspection Procedure was well documented, except for one error (on how to test resistance of the fusible link block at the 12V battery) which a more electrically savvy friend clarified for me.

I had already purchased a used DC-DC Converter Inverter Assembly off of ebay a few weeks ago (with a 6 month guarantee, free returns and free return shipping) just in case I did need to replace it. I had looked around locally, and could have gotten one for less than the $300 it cost (with tax), but local salvage yards don't even pull the part until payment is made (in person) and that would require me to make a second trip the following day to actually pick up the part. I would not even have been able to view the part while still installed in the donor vehicle. And, driving over 100 miles roundtrip, twice, through downtown Houston freeways was not appealing either. With a reputable ebay seller, I had a much better idea of what I would be getting. And the 6 month guarantee and free return shipping were the best I found anywhere.

A video I had found by CarHub showed the quick and dirty way to remove the assembly, complete with 4 letter language, but it was helpful in showing me what and how to remove, and the general sequence. I watched several times and made a written list of the steps involved. For my removal, I took my time, had on insulated gloves when necessary, and bagged and labeled bolts and clips at each stage. I did remove the coolant a little differently by simply wicking out as much as I could, using a long strip of an old chamois cloth. There was still some drippage after hoses were disconnected, but a drain pan would not have caught much anyway with all of the obstacles between the reservoir and the drain pan.

After old unit was removed, then took a little more time to transfer all but one of the metal attachment brackets from the original unit to the newly purchased unit (one rusty Phillips head screw wouldn't budge). Not sure of the mileage of the donor vehicle, but suspect it came from the northeastern US where the seller is located, based on the rusty condition of all of the brackets. And, swapped out the cover with my original cover, also in better condition.

Installing the new-to-me unit was just reverse of how I removed the old one, and only took about 1.5 hours (I work slowly). Filling the coolant reservoir, and researching how to bleed out any air bubbles, took almost as long.

Before powering up vehicle entirely, ran another Full Scan. Total of 14 DTCs found (4 different codes were: P3056, P0A09, P3000, and P3140) with all 4 showing up at least 3 times and with either a Current, History, or Pending Status. DTC P0A08 was not found. I had expected some DTCs to be detected. Sometimes the warning lights that appear will go away after a few start attempts. These did not. I had kept the 12V battery connected during the entire removal and replacement process, as the Inspection Procedure called for putting vehicle in IG-ON state for one test. The Toyota Removal Procedure DOES call for disconnecting the negative cable from the 12V battery before removing the Service Plug Grip, so I had missed that step. I now removed both the positive and negative cables from the 12V battery, waited about 30 seconds, and reconnected them. Voltage at battery was 11.56V. Put vehicle in IG-ON to do another full scan. No DTCs detected this time. Started vehicle and put in READY mode and all was well. Got voltage reading of over 13.5V at 12V battery indicating battery was getting recharged. Metered cable leaving DC-DC Converter with clamp-on meter and had high current flow of over 50A with several 12V items on (headlights, fan, defroster).

Finished re-installing all of the "trim" pieces that had to be removed to access the converter inverter, the 12V battery, etc. All put back together, and hope all continues to do well.

Thanks again to all who helped guide me to this conclusion, and hope my learning experience will be of some benefit to other owners.