The 12V source is a common junction point and the ground is provided by/in the PCM, your paralleling everything.

 

The key is that it must be across the coil. Of course, coils can be energized by switching the "Hot" ala the AC clutch coil or they can be energized by providing a ground to the "low" side of the coil.

Since there's no diode apparent in this circuit, one of two things would be assumed: 1) Any diode used is internal to the PCM or 2) there's no diode, so don't worry about it.

 

It's been some time since my military electronics training but I thought that the flyback diode needed to at the coil itself.

A search found the following:

To minimise the antenna-like radiation of this electromagnetic energy from wires connected to the inductor, the flyback diode should be connected as physically close to the inductor as practicable. This approach also minimises those parts of the circuit that are subject to an unwanted high-voltage — a good engineering practice.

A closer look my '09s diagrams showed all solenoids have polarity markings.

 

Can someone tell me why the following is happening?

Every 3rd day (like clockwork) my escape throw a po 455 code.

It doesn't matter how much gas is in the tank.

I clear the code, drive it to work the next day, no code.
Drive it to work the following day, no code.
Drive it to work the 3rd day, and I can tell you almost the exact mile/time the emission light will come on!

What gives!?!?!


Does the EVAP system only cycle every 3 day or what?

Thanks!

 

Certain system tests are only performed under certain conditions. So many drive cycles, idle time, speeds above a certain amount for so long, etc.

I was reading in my manual that certain EVAP test was run when the engine was OFF. It tests how long it held the vacuum.

 

I vacuum tested the purge valve today.

I took both inlet on outlet hoses off the valve

Put vacuum to the canister side of the valve first (8 hg), put a 12V source to the electrical connection and nothing happened.

Next, I put a vacuum to the manifold side of the purge valve, put a 12V source to it and nothing happened on that side either!?!

Is the purge valve bad? I thought that at least one side of the valve shouldn't hold vacuum while the other side should.

What's wrong?

 

Are you messing with the purge valve (the one on the firewall)? If so, why?

 

A DTC P0455 can be caused by a stuck closed canister purge valve.

 

I have had the vent solenoid valve off already and it held pressure and dumped after 12v was put to it.

I've checked everything else, so the last thing to check is the purge valve and the was the process of checking it I found on the web.

How about the tank's vent vapor valve

Or the (simple) check valve by the canister?

 

From my '09s manual, it states that the purge valve could be stuck closed, canister vent stuck open or the vapor vent valve assembly blocked.

 

When I tested the vent solenoid valve with a 12V source today, it closed fine.

But I notice when I blew air back up through the valve, I felt and hear air leaking out around the electrical connection (pins)?!?!

Should this happen? Is this valve bad then?

 

What about in the other direction or vacuum? It is a vent valve so it might not seal in one state although that doesn't sound right.

 

Bill,

When I blew through the vent valve when it open it seems fine, but if plug one of the end and blow through it, there's that leak around the electrical connection(pins) still.

 

It's open then so it shouldn't matter.

 

When I put a vacuum on the solenoid valve today, out of the car with power (12V), to close it. I hear the vacuum leaking around the electrical plug.

When the car's computer runs the leak test, it close the vent solenoid valve and puts vacuum to the system and sees how long it take the vacuum to decay. To short in time it would throw a po 455 code.

So I'm thinking the vent solenoid it bad.