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P0459 - Purge valve high voltage

Tiny
EMERSON HEIN
  • MEMBER
  • 2006 SUBARU FORESTER
  • 2.5L
  • 4 CYL
  • 4WD
  • MANUAL
  • 122,000 MILES
I am receiving this error code and alternatively will receive a P0458 (low voltage) code when I unplug the valve connector. Here is what I have done to pinpoint the issue:

- Valve was replaced and confirmed to function by bench testing.

- 12 olts is being sent to terminal 1 of the wiring harness.

- Valve will operate if I manually ground the valve to the chassis.

- Using the cars "test mode" I can see terminal 2 cycling between ground and open circuit, the valve however does not function.

- There is approximately 35 ohms of resistance when measuring between the two harness terminals with it unplugged from the valve.

- When I unplug the main wiring harness the resistance of the two terminals jumps to open circuit.

- I removed approximately five inches of protective cover from the wires to inspect for damages/shorts and none were found.

What I think is happening is an improper ground but do not know where the circuit ground point is located.
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Sunday, November 4th, 2018 AT 1:28 PM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,904 POSTS
The ground location does not matter if you have high resistance to ground just run a new ground wire. Here is a guide to help you test and the EVAP wiring diagrams so you can see how the system works and which wires to test.

https://www.2carpros.com/articles/how-to-check-wiring

Here are the engine and EVAP wiring diagrams. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Monday, November 5th, 2018 AT 4:09 PM
Tiny
EMERSON HEIN
  • MEMBER
  • 2 POSTS
Hey Ken,

Is the valve not operated by the ECM initiating a ground signal from pin number 29? Wouldn't running a new ground wire for the valve cause it to be permanently open as the blue/black wire sends 12 volts when the car is ON (aac). I believe the 12 volts comes from the main relay (see attached).

I will try and confirm the wires leading from the valve to the ECU are in good condition and re-read the amount of resistance on the yellow/red wire when the ECU operators the valve.
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Monday, November 5th, 2018 AT 7:51 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,904 POSTS
Yes, if they trigger the ground it will be open so don't do that. If the ECM is not closing the circuit it is bad. Check the wiring first though. Here is the location of the ECM, I would try to find a used one or get a rebuilt one that is programmed already.

Check out the diagrams (below). Please let us know what happens.
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Tuesday, November 6th, 2018 AT 10:05 AM

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