How is this relay coil being grounded?

Hello

Can anyone help me understand how this relay coil is being grounded?

I think the Park/Neutral switch is a pull-down switch input. The switch provides a ground for the relay coil, while also pulling the voltage down from the PCM?

1998 Dodge Neon.

Cheers

I see a feed from the fuse box to the park/neutral switch. The switch on the right goes to splice 106 which goes to pcm and relay. So we'd think this is a power feed.
Is there any chance of a page that's missing? Especially on the relay :huh:
Don't get me wrong I understand what you mean.

Yeah, that is kinda confusing, huh? I found this version of the diagram, makes things a bit clearer:



The park/neutral switch is definitely the ground in this circuit, but I think the PCM is simply monitoring voltage for it's own purposes. I would be surprised if the PCM was actually providing any voltage in this case, just an output state monitor.

The park/neutral switch grounds the relay and the switch provides an input to the PCM to indicate whether the transmission is in park/neutral, or drive .
this input is used to determine idle speed (varying with geat selection) and ignition timing advance.
the park/neutral switch is also used to cancel vehicle speed control.

here is a better diagram that shows the ground point at the very bottom of the park/neutral switch!

Tyler wrote:

Yeah, that is kinda confusing, huh? I found this version of the diagram, makes things a bit clearer

Thanks Tyler. Makes sense to me now.

Oh crap I didn't see your post jaivs26! Even better diagram

Thanks everyone.

So the Park/Neutral switch is grounding the control side of the relay. I would like to know how the PCM is monitoring the circuit. Is the PCM sending out 12v and watching it? Tyler mentioned an output state monitor - how does this work??

Don't forget to use the thank you button if the information was helpful.


Cheers.
Jaivs26

i think the computer only monitors the voltage or ground in the circuit..

Don't forget to use the thank you button if the information was helpful.

I'll give you a thank you. Good info!

ImBack218 wrote: Thanks everyone.

So the Park/Neutral switch is grounding the control side of the relay. I would like to know how the PCM is monitoring the circuit. Is the PCM sending out 12v and watching it? Tyler mentioned an output state monitor - how does this work??

Sorry sir, I could have been more clear :blush: In this case, I think the PCM is just using this relay control circuit as a input, monitoring the position of the park/neutral switch. It's watching the voltage, just like having a multimeter connected, and making determinations based on what it sees. 12V, for example, means that the ignition switch is in the Start position, but the park/neutral switch isn't closed.

I would be very surprised to see that the PCM is providing any voltage. To prove this, you could remove the relay and shift the transmission into drive or reverse, then monitor voltage on that circuit from the relay pin. If I'm wrong, please let me know!

Output state monitor probably wasn't the best term to use there, really, as I don't believe the PCM is involved in controlling this relay directly. My bad!

Actually, I take it back, there may be a bias voltage on this relay control circuit. I was initially pretty sure that it didn't, but then I remembered this video: