Just got another 09 Escape. It runs fine but it has the P0AA7 wrench code too. Don't want to replace the battery this time. Any idea where the sensor or circuit located?

 

This is that fun one again, where the recommended course of action is to:

1) Clear the codes
and if the code repeats...
2) Replace the HVTB.

Now, here's the interesting thing: In the 2011 Fusion, Milan, MKZ, Fusion Hybrid, Milan Hybrid, MKZ Hybrid Workshop Manual, instead of recommending replacement of the entire HVTB, they recommend replacing the Battery Pack Sensor Module (BPSM).

http://www.nicksmustangranch.com/Ser...l/sbse3009.htm

This code has to be generated by a similar module that is not named on the FEH. Would that be inside the BCM? You've already shot this bug before by replacing the BCM. Maybe it will work here, maybe not.

I can't find anything that shows where the exact circuit is that causes this code to be thrown. The code itself refers to the system making sure that the HV system is totally isolated from the rest of the vehicle.

How to troubleshoot it? There's a pretty good article here - at least in explaining what the code means. Diagnosing it and pinpointing the loss of isolation is another story.

https://www.vehicleservicepros.com/s...-fault-systems