Voltage scanner is reproting doesn't match actual value

[walt6076]

I'm adding a GM MAP sensor to log boost and having an issue where the voltage I measure at the EIO connector doesn't match what the MPVI is seeing. When I measure voltage at the EIO connector pin using the ground pin in the MPVI I see 2.10 volts. I'm seeing 2.16 at the sensor itself so I'm assuming there is just a slight difference in ground offset between my sensor and the ODB feed to the MPVI. I've defined the Transform Functions as " (Input / 1 ) + 0 = Output." That should just log whatever the voltage is, right? But I'm seeing 3.75 V in the scanner.

How does 2.10 get to be 3.75? Until I get this right there isn't much point trying to put in the calculated transfer function for PSI.

I have verified the same behavior one EIO input #2 and input #3.

And I have verified that there is a connection, higher input V does produce a higher logged V, they just never match.

[schpenxel]

Why do a transform at all if you only want to see the voltage? Without doing any sort of transform you should just get voltage..

Remove the transform (just add the input to the channel list) and see what voltage it shows

Do you have a ground for both the MPVI and MAP sensor running to the same source (battery preferably)?

[walt6076]

Deleted the custom PID again; rebuilt it from scratch again; works OK now. Cannot explain it. Not going to try to explain it.

[schpenxel]

Sometimes that is the best way