Failed High Voltage Battery

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The P0A0A is an interlock circuit code. From those technician comments, they found an open circuit inside BOTH High Voltage batteries. That doesn't sound likely. The working "between both upper and lower packs" would be related to the High Voltage wiring harness (orange cables and connectors). A new harness is around $1,800 retail, plus labor. The lower pack does need to be removed/ lowered to replace the harness. I just did my harness and it wasn't that hard.

How do you feel about checking it out on your own?
Yeah, sounds like a "We ran the checks in the manual and couldn't figure out the cause. Money please"

Critical thinking and troubleshooting isn't really a part of vehicle servicing anymore, sadly.

If you do swap your harness, I will buy the bad one from you.
I found the 2014 battery removal guide online. On page 7 it has COMPONENT LOCATION AND IDENTIFICATION section. What wiring connection are you referring to. Are we talking about #3 on the list. The High-Voltage Wiring.
I was thinking you could double check the HVIL loop to see where the open circuit is. If it's truly internal to the battery you should be able to verify that. Otherwise, it's a connector or harness issue. The wiring diagram (Cell 12, page 10) and Workshop manual 414-03A Pinpoint test step A7 should make sense and show you where to check. Essentially, the entire circuit has to be complete /no open circuit. Please forgive me, I can't seem to figure out how to upload the PPT or wiring information referenced.
If it is a P0A0A at the BECM, there are 5 points that you need to check. In the HV connectors, there will be 2 little pins that interface to their mating connectors. As mentioned, it is just a loop through all the HV connectors to make sure the connectors are secured.
-Check the HV disconnects. There is one behind the back seat and another by the passenger side rear tire. There was a TSB to apply some dielectric grease so the connections don't corrode. So check for that. But also make sure the pins are not bent. Then make sure that the are fully engaged. Sometimes it can look engaged but it isn't. With the disconnect engaged, pull as hard as you can to pull it out and it should not budge if it was engaged correctly. Note that there are 2 interlock connectors on these disconnects, but I think only one side is actually active.
-The 3rd interconnect is just to the right of the disconnect behind the back seat. This isn't a is just a cover; but it still has an interlock connector on it. Again, unbolt the cover and check that the pins are straight and greased.
-The next connector is at the driver-side rear tire. These can be brittle, so be careful when engaging and disengaging the clamping lever. Pull the connector back and check the interlock pins as the previous 3 connectors.
-The last one is a connector just like the previous one. It can be brittle and you need to be careful with the clamping lever. Check that the interlock pins are straight and greased.

If that doesn't work, then you might need troubleshoot the internal loop. I think it is possible but not as easy. Inside the upper battery pack where the BECM lives, I did find one end of this loop but I didn't find the other. Not much is documented inside the battery pack, but I can confirm that the one end of the BECM that I did find, the first connector in the loop is the disconnect behind the seat. It is the interlock connector on the right side that is active and then it chains to the HV cover that sits right next to it. From there, I don't know where the next connector is, but with a multimeter and some help and patience, you might be able to figure it out.

There is a similar loop at the front of the car under the hood. I'm not sure which module reports that interlock issue, but I don't think it is the BECM.
Of. Course. Ford called back stating that the vehicle is out of warranty and that they are no programs available or recalls for the vehicle. They stated I am on my own to pay for the vehicle repairs. Now I have to see what it’s going to cost to get the vehicle out of the dealership service department.

Once I get the vehicle back I’ll see what I can diagnose and update.
2014 Ford focus electric died with 36000 miles on it

I was at the fitness center, came out, got that nasty red triangle. and my car was inoperable, Had it towed to dealer and after a few weeks, they came up with this: ( shortened)

Ran DTC's and found POAAO:01 to be related. Ran pinpoint test. Advised to clear DTC,s and retested for DTC,s Found to return Started pinpoint test K. Ran self test on TCM, dc/dc inverter, and SOBDM. Found P0C78 to be current in the BECM. Checked at both battery connectors for high resistance, short to ground, short to voltage. Found all to be good. Had to depower the high voltage battery system. Had to check for continuity from the TCM to the DC/DC converter module. Found to be good. Checked for short to each other in the in the DC/DC converter module shields and found to be shorted together. Need to replace harness to continue, replaced harness, still inop, Will require replacement of battery (cm6z10b759tarm)

Now the (blankety blank) dealer wants 826 dollars for their effort! Whoops I forgot, they want $21000 for a new battery.

Is it me, or are their " pinpoint" tests not very precise!?

Any ideas what this could be?

New member... Ray ( sorry about the long description )
I guess I should go where you went. It’s cheaper.
$800 for labor. $24k for battery plus labor. Luckily the $800 goes towards the labor. But I can save a few k. Lol
famsail5 said:
Is it me, or are their " pinpoint" tests not very precise!?

The service manual has a list of test operations that eliminate various pieces. Each step is a "pinpoint test", usually in ascending difficulty/cost.

In this case each step kept moving toward the battery. And since the internals of the battery are not serviced, that's as far as it goes. "We've isolated it to the battery and all we can do with the battery is replace it"

If they replaced your harness, get the old one unless it's required for a core fee.
So, I went to my Ford dealer and they printed out what I guess is a work record. It has some more DTCs on it. Does anybody have any info on what they would mean? I didn't think DTC info was publicly available. There was no anti-freeze visible under the vehicle, and the coolant bottle was still half full. The mechanic said he had no indication that fluid had leaked into the battery. The DTCs are: B1215:, P0C78:, B12D8:, B12DC:, P0AA0:

The work record has the sequence the mechanic used, connectors he used and sometime their location if that helps

Any ideas?

There you go! (From the service manual)

B1215:00 External Memory Card: No Sub Type Information Set by the APIM when it detects a device conflict through the media hub, a fault in the USB cable or media hub, or there is no navigation Secure Digital (SD) card present.

Do you have, or did you have something plugged into a USB port?

P0C78:00 Hybrid/EV Battery System Precharge Time Too Long: No Sub Type Information Before closing the positive contactor, the BECM first closes the precharge contactor. The BECM monitors voltage leads attached to the high voltage battery internal circuits to verify that the precharge contactor closes when commanded. A fault is indicated when the BECM is receiving data that indicates the precharge contactor did not close when commanded. When this fault is set, the BECM does not allow the vehicle to restart and the powertrain malfunction (wrench) warning indicator is illuminated in the IPC .

This is why you got the wrench icon. Could be a bad precharge contactor, a poor connection at or in the upper battery, a low isolation event, or something else.

B12D8:11 Mirror Heater Output: Circuit Short To Ground This Diagnostic Trouble Code (DTC) is set if the Driver Door Module (DDM) or Passenger Door Module (PDM) senses lower than expected voltage on the mirror heater circuit.

This could be mirror heater wires rubbing on the body metal.


B12D8:15 Mirror Heater Output: Circuit Short To Battery or Open This Diagnostic Trouble Code (DTC) is set if the Driver Door Module (DDM) or Passenger Door Module (PDM) senses greater than expected voltage on the mirror heater circuit.

This could be the mirror heater disconnected, or burned out.

B12DC:02 Front Window Motion/Position Sensor: General Signal Failure This DTC sets when the PDM detects a concern with one or both of the Hall-effect sensor circuit(s). When this DTC is present, the front window will only operate in short steps.

I believe the Hall-effect sensor works like a tachometer, pulsing as the window goes up or down. Its not pulsing at all. Could be a disconnection, a motor not running, a wire rubbing on body metal, the window stuck, the Hall-effect sensor broken, or other.


B12DC:54 Front Window Motion/Position Sensor: Missing Calibration This DTC sets when the DDM or PDM has lost calibration data. When this DTC is present, the front window will not have one-touch up or one-touch down functionality.

This is most likely caused by the B12DC:02. The car doesn't know the position of the window. If the window motor and mirror harness are bundled together, they might be rubbing on the body metal.

P0AA0:01 Hybrid/Ev Battery Positive Contractor Circuit: General Failure CARRY OUT the BECM self-test and DIAGNOSE BECM Diagnostic Trouble Codes (DTCs). REFER to the BECM DTC Chart.

This is because of the P0C78.

Only the P codes would prevent your car from driving. And the P0C78 is the likely culprit.
The service manual has a lot of Pinpoint K tests to do for a P0C78, I wonder if the dealer did any of them?
for fun, I checked the P0C78 code on line, and it seems that for GM vehicles, the code has the same meaning, and they have a bulletin, that says to check the continuity of the fuse in the high voltage disconnect.

Thats an easy check
Leaking coolant seems to be such a common problem that a class action would be worth at least looking into. Battery packs should not be failing before 100k miles.
So thanks Anti_Climax and Heima for the info. The high voltage disconnect had 0 resistance, so I guess I'm not that lucky. Does anybody know how hard it is to get a precharge contactor. Any advice on repair manuals? I can't believe those 12.95 repair manuals on e-bay are worth much