I found a problem with the IMRC board and I think this could be a common cause of P1518 Check-Engine code.
Thanks to the write up of the following members and it was a great help in finding the problem and removing the IMRC module for repair (I don't even have the repair manual ! Any one has the eManual that can share? )
This is what I found:
After I removed the IMRC with the instruction of the helpful links above. This is the IMRC circuit board:
The arrows are pointing to the problematic area on the other side of the board.
When you turn over:
Circular cracks found on the solder joints of the relay leads. They are pressed by the rotating cam every time you start the engine and when you rev >5000 rpm and back. Eventually the slight mechanical force is causing circular crack on the solder joints and created a bad electrical contact (weather/temperature dependent and that's why this problem sometime is intermittent )The cold Boston weather probably has contributed to the problem since cold solder joints are less flexible and might crack more easily.
Zooming in to the solder joints:
The same circular cracks from a different angle:
I used my beloved soldering iron to reflow the solder (with added fresh solder) on the joints and the problem was solved. It's been a week after my fix, no more P1518 and also have got my inspection sticker finally (I did drive my car for 85 miles after reconnected the battery and have enough time for the sensors to capture readings before the re-inspection).
This is not the first time I saw this kind of problem. This is a well known problem of Honda/Acura Main relay module. This is another DIY that I wrote fixing a similar circular crack problem in the Acura Legend forum (again circular crack on relay lead).