Normally there are multiple clacks, (negative contactor and pre-charge contactor, then a delay, then pre-charge contactor dropping out and positive contactor engaging) are you sure you're not hearing any at all? That would suggest quite a different problem of the ECU not even pulling in the contactors at all.sorry can no longer hear any clacks when turning key to start.
Have you tried disconnecting the HV cables to the PTC heater and A/C compressor as a quick test to rule out an insulation breakdown or fault in those? These are the two connectors at the front of the battery pack separate from the cable going to the MCU, and you only need the underbelly plastic covers off to get at them.
P1A15 means the high voltage (measured at the MCU I think) failed to rise to the expected voltage within the expected time period of a few hundred milliseconds during pre-charge.
There are many possible causes for that including -
1) Contactor didn't close at all due to the 12v feed to the contactors not being applied. If you really don't hear any clicks this could be your situation, in which case start tracing the control signals from the ECU. (Are the i-Miev circuit diagrams adequate for this?)
2) Burnt contactor contacts or faulty pre-charge resistor. (Both inside the battery pack)
3) A parasitic load on the HV voltage lines beyond the contactors - this could be in the PTC heater, A/C compressor, MCU or OBC. The PTC heater and A/C compressor can be isolated as above, and it's also possible to isolate the OBC DC/DC converter by removing the 20 amp fuse in the MCU inspection hatch at the top. It wouldn't take much load for the pre-charge resistor and parasitic load to form a voltage divider which prevents the target voltage being attained during pre-charge.
4) A fault with voltage sensing in the MCU, where it detects a lower than true voltage. We've seen a couple of examples of this on my-imev.com and there is suspicion that the voltage divider resistors may be drifting in value. I think one person padded the top divider resistor with a high value and managed to resolve their issue that way.