Park/Neutral signal switch wire voltage

[srobertsfsj]

I was doing some troubleshooting today and noticed that my park/neutral signal wire was putting out 12v. Looking at the connector reference chart on this site the voltage should be 0 in both key on and run. Why would mine be 12v, that has me a little worried....

[EagleMark]

IIRC you wired this into the Jeep column?

If you data log with TunerPro most ADX files have an entry for Neutral or Drive to see what it is doing.

[srobertsfsj]

Right now I dont have it wired at all as I was having high idle issues in park. According to this sheet it should be 0v since it is a signal wire? Wire B10

http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1940&d=1331599730
(http://www.gearhead-efi.com/Fuel-Injection/showthread.php?304-1227747-ECM-Information-42)
I am trying to figure why the Jeep just died yesterday on the way home, would start for about 30 secs and die, did this a couple of times and luckily I was just a block from my house when this started so I was able to get into the driveway. I know this could be a million things but I am trying to trouble shoot. I had this wire just lying in the engine bay loose because I didnt think it had any voltage to it.

[EagleMark]

In looking at wiring diagram I was wrong and the test is wrong and it should be 12 volt?

http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1936&d=1331599707

[EagleMark]

7747 will always have high idle issues in park neutral, this one always confuses me because it's 12 volt and supposed to be to ground for drive. So most conversion just ground it.

[srobertsfsj]

Thanks Mark, that makes me feel better about the output of the wire but leaves me no closer to figuring out my issue. I was hoping this wire was accidentally touching metal and shorting out the TBI. I guess that one thing eliminated from the list at least.

[jameslleary]

My P/N switch, that I obtained from an 87R/v truck only has a prong for ground, nothing for a 12volt feed. shure that 12v in the diagram is not a footnote?
TP indicates Park and in gear just fine.
I would hate to see someone hook voltage up to it, and maybe fry the ecm!

[EagleMark]

If it was shorted you would have lower idle and steadier in drive... not sure that is your issue though?

[srobertsfsj]

My P/N switch, that I obtained from an 87R/v truck only has a prong for ground, nothing for a 12volt feed. shure that 12v in the diagram is not a footnote?
TP indicates Park and in gear just fine.
I would hate to see someone hook voltage up to it, and maybe fry the ecm!

Just like you mine is a grounding type P/N switch, that may be why i had problems with Park idle speed.

[jameslleary]

Just like you mine is a grounding type P/N switch, that may be why i had problems with Park idle speed.I wish there was a way to confirm what the "12v" is on the digram. I just looked at my P/n switch to be sure, and the only other thing thats on it, is the feed for the reverse lights.

[Six_Shooter]

This is an electrical property. There should be a pull up resistor inside the ECM on that pin, that will help the processor see a change from 12V to ground. This generally works more reliably cor detecting a state change than going from floating (niether ground nor positive) to ground.

[srobertsfsj]

This is an electrical property. There should be a pull up resistor inside the ECM on that pin, that will help the processor see a change from 12V to ground. This generally works more reliably cor detecting a state change than going from floating (niether ground nor positive) to ground.

Great explanation, I didn't know any circuits worked like that. Thanks Six Shooter!