+12V pins in the ECU connector? What is Diag line RXD?

[grr]

I'm checking the ECU connector for correct +12V pins after an engine swap just to be sure not to fry the ECU..

I found this:

Pin 13: Diag Line RXD +11V
Pin 18: Power Input +12.9V
Pin 36: Main Relay Control + 12.9V

What is the Diag Line RXD, and is it supposed to be 11V?

[zygoteer]

It is in fact an RS232 receive data line, meant for serial communications to a diagnostic device (laptop mostly).

Don't frig about about with that line except using the correct diagnostic interface.

However, in a quiescent state they are usually pulled high - nominally 12v, but usually less a diode + transistor volt drop (i.e. about 1.1 to 1.5 V down).
RS232 interfaces that read these signals are not usually fussy about voltage - most will accept voltage swings down to about +/- 5V and some tolerate + voltages only, but it has been known to get unreliable then.

[grr]

Thanks! Sounds like it's just how it's supposed to be then?