Probing 'unused' ECM pins

[blindsquirrel]

I'm building a bench harness to go a-pokin' around at unused pins to see if anything interesting shows up. Don't want to fry anything if I can help it. Anybody have safety tips? I don't know how useful it would be to check first for voltage/ground, as the pins could have pullup/pulldown resistors inside and might lead me astray. An unused signal pin probably won't be truly isolated from everything on both sides.

What's the 'safe' way to check them? Jumper a 5v source through some value of resistor?

[RDF1]

I'm building a bench harness to go a-pokin' around at unused pins to see if anything interesting shows up. Don't want to fry anything if I can help it. Anybody have safety tips? I don't know how useful it would be to check first for voltage/ground, as the pins could have pullup/pulldown resistors inside and might lead me astray. An unused signal pin probably won't be truly isolated from everything on both sides.

What's the 'safe' way to check them? Jumper a 5v source through some value of resistor?

Were you able to try anything on this?

[blindsquirrel]

Nah never went any further. Being that reading a voltage would be dependent on both the OS supporting it AND having some kind of PID defined for it in the scanner, odds of finding anything would be extremely low.

My E40 even has one for the brake booster sensor that reads just fine in other scan tools, but there's no PID for it in the HPT scanner. Support said they'd look into adding it but since that was like 2-3 years ago it'll never happen.

[RDF1]

Ahh!
Ive got a couple E38s if you wanted to use them and if you fried them then no loss.

[verlon]

Ahh!
Ive got a couple E38s if you wanted to use them and if you fried them then no loss.

I've already probed and traced lobotomized E38.

E38 Complete Pinout.pdf

[STL_G8GT]

Bringing this one back from dead... In looking at your complete pinout for the e38, does anyone know if unused 5 volt reference and low reference ECM pins are live even if the specific vehicle OS doesn't call for the use of those pins? Example if pin #x is for the five volt reference for a clutch pedal position sensor, but the car is an automatic, would that pin provide 5 volts if you added a pigtail to the terminal? Or does that option need to be turned on for that output to be live? It looks like there's two 5 volt circuits, are all pins live at all times for those two?

[verlon]

Bringing this one back from dead... In looking at your complete pinout for the e38, does anyone know if unused 5 volt reference and low reference ECM pins are live even if the specific vehicle OS doesn't call for the use of those pins? Example if pin #x is for the five volt reference for a clutch pedal position sensor, but the car is an automatic, would that pin provide 5 volts if you added a pigtail to the terminal? Or does that option need to be turned on for that output to be live? It looks like there's two 5 volt circuits, are all pins live at all times for those two?

Low reference and 5v reference pins are live all the time, they are hardwired.

[STL_G8GT]

Low reference and 5v reference pins are live all the time, they are hardwired.

Thank you for your help - I ended up using the unused cpp sensor wires for 5v and low ref - worked great. Thanks for the knowledge!!