Thanks, it's an idea but it's not actually fixing my problem, it would merely be taking the reading before the voltage drop and ignoring that the ECU is reading low. I have to actually double check my ecu voltage just to confirm it's reading on the low side, just because the secs goes between 11-12.7 I need to physically check at the ECU that this is right.
If indeed I'm getting +13v at the ecu and the SECS is just displaying a different figure i'll rewire it like you have done so It reads accurately.