Oil Pressure Valve Solenoid - Subaru Outback - Subaru Outback Forums
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post #1 of 14 (permalink) Old 10-24-2012, 11:47 AM Thread Starter
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Oil Pressure Valve Solenoid



Hello all, I have a 2008 Subaru Impreza Outback Sport AWD 2.5L SFI SOHC 4cyl

I am searching for a DYI service manual. I looked for a chiltons or haynes but no luck.

I received a P0028 code and the book refers to this as an Oil Intake Valve Solenoid.

The dealer told me it is called an "Oil Pressure Valve Solenoid". They priced it out at $139 and it looks easy to replace on bank 2, (the drivers side).

Does anyone know how to test this valve to see if it is actually malfunctioning?

Or could it be the Oil Pressure switch that works in conjunction with the Oil Pressure valve?

Does anyone know of a DYI service manual, eg. Chilton, Haynes?

Thanks and Regards.

osowskig
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post #2 of 14 (permalink) Old 10-24-2012, 12:39 PM
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I recommend alldatadiy.com. You pay a yearly subscription but the information is equivalent to the Subaru FSM. Should contain a diagnostic procedure for that code.
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post #3 of 14 (permalink) Old 10-24-2012, 03:05 PM
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The P0028 code is set when the pressure sensor switch condition (closed, open) does not correspond with the duty cycle signal that's being sent to the related solenoid.

The solenoid controls oil pressure to the variable valve lift cams while the pressure sensor checks to see if the pressure is, in fact, high when it should be high and low when it should be low.

The troubleshooting tree starts out by checking the wiring between the engine control module and the pressure sensor switch, rather the solenoid. Presumably the idea is to make sure that the pressure sensor function is okay, and after that, presume that the fault must be the solenoid.

There have been cases where the pressure sensor switch failed -- in some the sensor was (visibly) leaking and wouldn't respond properly to the actual oil pressure.

The solenoid, of course, could also fail to function properly; however, if there were an open or short in the solenoid or the wiring to it, that would generate a different trouble code.

This post (My 2007 Outback is leaking/Burning Oil - Subaru Outback - Subaru Outback Forums) has a good photo of the left bank solenoid (on a 45 degree angle) with the aqua/pale blue connector, and the pressure sensor vertical to the left of the solenoid with the white connector. (Read down for cautions when installing the switch, and to post #19 for another P0028 case caused by the pressure switch, not the solenoid.)

Last edited by plain OM; 10-24-2012 at 07:20 PM. Reason: correct
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post #4 of 14 (permalink) Old 10-24-2012, 03:19 PM
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Got the same code shortly after an oil change. I was in a pinch and had to use a Walmart filter. Changed to a Purolator filter and cleared the code. Code has not returned. Maybe a fluke, maybe not. Just putting it out there incase others get the same.

My other car is a Subaru.... Come to think of it, so is my other other car
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post #5 of 14 (permalink) Old 10-27-2012, 02:24 AM
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Hi,

I have just started to explore the possibilities of romraider and freeSSM - what a revelation !

This issue can be monitored and logged very easily with romraider.

The ECU command for the inlet valve lift (solenoid) is "VVL Lift Mode (raw ecu value)" and the responses from the pressure sensors are "Engine Oil Pressure Switch #1 (On/Off)" and "Engine Oil Pressure Switch #2 (On/Off)".

When the command changes from 1 to 3 the pressure sensors should both go from 1 to 0. Do your log and you can trend the values either against time or any other parameter .

It's a good start for further diagnosis.

Kind regards,

Tapani
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post #6 of 14 (permalink) Old 10-27-2012, 01:00 PM
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Quote:
Originally Posted by Wagondude View Post
Got the same code shortly after an oil change. I was in a pinch and had to use a Walmart filter. Changed to a Purolator filter and cleared the code. Code has not returned. Maybe a fluke, maybe not. Just putting it out there incase others get the same.
interesting! A co-worker reports that aftermarket filters are known to cause a similar problem in Mercedes-Benz's .

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post #7 of 14 (permalink) Old 10-27-2012, 01:01 PM
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Quote:
Originally Posted by Tapani View Post
Hi,

I have just started to explore the possibilities of romraider and freeSSM - what a revelation !

This issue can be monitored and logged very easily with romraider.

The ECU command for the inlet valve lift (solenoid) is "VVL Lift Mode (raw ecu value)" and the responses from the pressure sensors are "Engine Oil Pressure Switch #1 (On/Off)" and "Engine Oil Pressure Switch #2 (On/Off)".

When the command changes from 1 to 3 the pressure sensors should both go from 1 to 0. Do your log and you can trend the values either against time or any other parameter .

It's a good start for further diagnosis.

Kind regards,

Tapani

I hate buy another cable. Will SSM work with a Tactrix cable?

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Fruit Flies Like a Banana!
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post #8 of 14 (permalink) Old 10-27-2012, 01:36 PM Thread Starter
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Quote:
Originally Posted by Tapani View Post
Hi,

I have just started to explore the possibilities of romraider and freeSSM - what a revelation !

This issue can be monitored and logged very easily with romraider.

The ECU command for the inlet valve lift (solenoid) is "VVL Lift Mode (raw ecu value)" and the responses from the pressure sensors are "Engine Oil Pressure Switch #1 (On/Off)" and "Engine Oil Pressure Switch #2 (On/Off)".

When the command changes from 1 to 3 the pressure sensors should both go from 1 to 0. Do your log and you can trend the values either against time or any other parameter .

It's a good start for further diagnosis.

Kind regards,

Tapani
Hi Tapani,

May you please recommend a USB cable to work with the FreeSSM software and USB interface? I saw the VAG-COM recommended but strangely enough the Subaru is not listed as being supported. Maybe I have the wrong link. I do not know a lot about the ECU, do you know which type is in the Subaru?

Thanks and Regards,
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post #9 of 14 (permalink) Old 10-27-2012, 02:40 PM
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Using FreeSSM in this case will not tell help you resolve this issue.

If the ECU commands pressure and the sensor does not detect pressure then you still don't know if the switch if bad or if the pressure sensor is bad.

The only way to resolve this without guessing is by hooking up a oil pressure gauge at the same location and measuring pressure when the ECU commands pressure.

If it was me, I would go with the one that more commonly fails which is probably the switch. I am not speaking from experience with this switch though. You could also probably take the switch off and test it.
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post #10 of 14 (permalink) Old 10-27-2012, 05:37 PM
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That's right. The OBD has already determined that the pressure switch status isn't consistent with what the solenoid should be doing. That's about all FreeSSM and RomRaider Logger can do as well.

There are separate DTCs (diagnostic trouble codes) for a short or open circuit to the solenoid, which could cause it to malfunction, but there's no diagnostics to detect, for example, if the solenoid is mechanically stuck open or closed and not responding appropriately. The pressure switch will tell if the pressure is wrong, but not why. Moreover, if the pressure switch fails, there's no DTC for it, other than the one already indicated.

[Oil Pressure Sensor Switch – how it “clicks” might be of interest. Although it's about the engine oil pressure switch, they're pretty much the same as far as physical design and function.]

Check for signs of oil seepage around the pressure switch. This is usually an indication that the switch is failing, if not already inoperative.
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