i have almost completed a trace of the ISA board. The final and biggest unknown is the part number/identity of the little 5-pin device on the top near the transformer and op amp.
i'm guessing that it is some kind of dual voltage regulator in an SOT 23-5 package, but the part has been etched on my board and no markings could be read. There is a via off of pin 4 that is an important control input signal to a chip on the bottom side.
Could you please take a look with a magnifying glass to see if you can read a part number? Anyone else with an open MCU control board?
On the top side is the AD8677 op amp, the 5-pin device, 2 transformers (1 signal and 1 for power), a Toshiba 4066 Quad bidirectional switch., and a 3 pin zener diode device. On the bottom side there is another 4066, a 3-pin dual diode, and a TL494 PWM power supply controller chip. So if would be possible to make custom boards if these are suspect and a vendor for the ISA215-HYB cannot be found.
A picture of the ISA board pinouts has been shown in other posts but i will list it here: 1 = VH; 2=VL; 3=Output Signal; 4=Gnd; 5=12V supply.
The P1A15 error code will be generated if that pin 3 signal (0-5V range) is not meeting the necessary ramp-up conditions that the EV-ECU is expecting.
So a fault in any of several parts on this little bitty board will disrupt or degrade the pack HV reading and brick the car. i think we could come up with a way to test this board on the bench with a power supply and oscilloscope. It has no reference designators so we will make up our own.
A quick look seemed to show that this pin 3 signal is sent to the MCU microcontroller; will trace it all the way when i get some free time.
Here is a markup of the bottom side