The P1A16 Error Code Repair

[FusionAZ]

Just wanted to do a quick DIY repair thread on the P1A16 error code (usually accompanied by a bunch of other codes that lock out the battery).

 

 

 

So it turns out that the coolant pump for the inverter/transaxle was weak and or failing. In my case it was moving water just not well and it had burnt up my inverters (Car is located in a hot climate). Per the PC/ED supplemental manual it states you will need to replace the whole transaxle on the car. I ended up buying a used transaxle (the shop accidentally split the unit in my case). They also dropped the gear portion so I ended up getting the inverter portion that I needed (at an extreme discount). In most cases you will need to buy the whole transaxle since it is a "sealed combo unit". If a shop is not that bright and split it they are obligated to sell you the whole thing since it is just one part number (or ask for a discount). This is not a Prius or newer gen Fusion/Lincoln where its a separate unit.

 

I have linked screenshots from the online manual offered by https://www.nicksmustangranch.com/. The P1A16 code specifically means the inverter is toast. If you like to wrench in general on your car Nick has the most comprehensive interactive online Ford Manuals (just requires a donation for access). He does it as a hobby and I have found the service manuals and diagnostics to be extremely helpful.

 

 

***WARNING SIDE NOTE****** Before taking on a project like this realize this is a high voltage system and it can kill you. Follow all proper procedures and guidelines to stay safe and you will be okay. I pulled the high voltage disconnect for the car. To double check I used a voltmeter before proceeding to verify the voltage was not present. You can also get high voltage gloves. I also disconnected the 12v battery as well.  

 

With that disclaimer out of the way regarding safety.  Here are some general photos with lots of steps not shown.

 

Quick Rundown:

-Remove cover

-Disconnect all wire harnesses and pull aside (be sure not to crimp or damage)

-Remove circuit board and its attached bracket

-Remove all bolts holding on the inverters (do no let them fall into the car when reinstalling)

-(Optional) Ohm the 3 phase motors while you have access to make sure the transaxle is good

-Remove the Inverters keeping track of where the units go (Doner to Car)

-(Optional) Get some computer thermal compound and put it on the bare spots (I did not remove the paste). Or buy industrial thermal compound (Probably overkill).

-Reverse installation of the inverters

-****KEY POINT*** Install the cars existing circuit board or the car will NOT start and be immobilized

 

-REPLACE THE COOLANT PUMP FOR THE TRANSAXLE

 

Some Photos of the process:

 

Here is the inverter in the car with the cover still on. I had started to remove the reservoir at this point.

 

 

I have removed the cover on the inverter. The green circuit board needs to go back into the car and not the doner board. So set it aside and make sure it does not get damaged. Super important or your hosed.

 

As you can see I moved the attached wires to the side to not get damaged. I then removed the bracket that held on the circuit board. I removed all the hex head bolts on the inverters and unplugged the wires shown.

 

 

 

This is the doner car's inverters. It looked like the first picture and had the board and all the other parts. I removed everything but left in the inverters until I was ready. This is crucial since you do not want debris between the thermal paste and the heatsink in the car.

Just a side note and tip leave all the metal plates on the old inverters and new ones. You will have to loosen them but do not remove to just make life easier.

 

 

Here is a closeup of the used inverters. You can see how I left the tabs on. 

 

 

 You will also need to replace the water pump for the inverter/transaxle. If you go on eBay you can buy a genuine Engine Auxiliary Water Pump Bosch 0392023014. It is the exact same pump and you can install it in the stock Ford bracket. This is much cheaper than the $$$$$$ Bosh part with the Ford part sticker on it (I just transferred the sticker over).

 

 

 

This is not for the faint of heart but if one has some mechanical knowledge it is doable. Just have to be safe and take your time. Also, change the transaxle fluid to prolong the life of the transmission.

 

 

 

Edited December 4, 2023 by FusionAZ

[WKelley]

I understand why, but I would also never recommend anyone that is not EV certified touch that battery or the components because of the sheer amount of voltage that could be present.  Your writeup is fantastic though.  I've been a mechanic for 30+ years and I stay far away fro EV/Hybrid systems as I just neve cared to learn it or felt the need to work with the dangers, I leave that for the younger techs that have the know how and ability.

[FusionAZ]

19 hours ago, WKelley said:

I understand why, but I would also never recommend anyone that is not EV certified touch that battery or the components because of the sheer amount of voltage that could be present.  Your writeup is fantastic though.  I've been a mechanic for 30+ years and I stay far away fro EV/Hybrid systems as I just never cared to learn it or felt the need to work with the dangers, I leave that for the younger techs that have the know how and ability.

 

Thanks for the positive feedback on the write up. This was much more affordable and easier than trying to pull the whole transaxle from the car. I would agree that a "trained professional" when it is out of someone's scope of practice is the most viable option. If someone does not know how to de-energize a high voltage traction battery system they should not be working on it. I am not a trained professional but I have a fundamental understanding of how this system works and how to work on it. 

 

Side Note: No shop will just take the guts out of a transaxle and put the guts in. They will require a new transaxle to be put in.

Edited December 5, 2023 by FusionAZ
side note

[beforeburner]

Hey, thanks so much for the writeup!  Is this still working well for you?  I have a similar issue with a p0a78 code.  How did you isolate the problem to the inverter instead of the battery?  I'm trying to determine what may need replacement in mine.  I'm also wondering if replacement of just the coolant pump may work?