[donvnod]

Did the job today. When I took out the old switch and measured it (primary contact to threads) the resistance was ~5 ohms. I was going to try re-installing it and checking the reading in place but the switch tumbled onto the ground. After that it read open - tried tapping it, etc. - no change. So that's that. I did take a photo so folks can see how few threads are engaged from the factory - and those threads looks shiny bright. I don't see any way to post the photo here, unfortunately.

The dealership paperwork stated they had removed the switch and cleaned it... the photo seems to tell a different story, or we have a different idea of what clean is. ;-)

Anyhoo, installed the new switch (finger tight and then just to the same rotational position as the prior one) and it tested to the same nearly zero ohm value when in place. No leaks and the fault code has stayed clear in a couple of brief rides.

 

[donvnod]

OK, let's try this...

 

[awd4me]

Measured the resistance on the oil pressure sensor switch on bank 2 where I had the P0028 code appear.
Readings were taken with a semi-cold engine, and fluctuated in a rising pattern, anywhere from 16 to 33 ohms, with a 39 in there somewhere. Since there wasn't a steady reading, I just ordered a Subaru switch which I hope will resolve the problem.

 

[plain OM]

If you are dealing with the P0026 or P0028 codes, and the switches are good, or have been replaced without improvement, look at this more recent thread:

https://www.subaruoutback.org/threads/avls-filter-and-p0026-p0028.509227/

A blocked AVLS housing screen, or a piece from a broken screen could also cause the codes.

 

[Bruce Nelson]

To add data:

21 ohm - Old switch. Appears to be aftermarket brand. No leaking. Thought it may be the cause of P0026 but turns out the switch was probably still functioning.

7 ohm - Old switch. Aftermarket. Functional. No leaks.

< 2 ohm - New OEM switch

 

[plain OM]

21 ohm - Old switch. Appears to be aftermarket brand. No leaking. Thought it may be the cause of P0026 but turns out the switch was probably still functioning.

Findings in post #56 might provide an explanation, namely, that the switch resistance would have to remain fairly high (~400 Ohms) when it should be low, for the OBD to conclude there's a fault.

 

[dyqik]

Findings in post #56 might provide an explanation, namely, that the switch resistance would have to remain fairly high (~400 Ohms) when it should be low, for the OBD to conclude there's a fault.

A quick reminder about my experience four years ago with this: I had a switch that measured around 20 ohms, but would miss the high pressure intermittently, enough to set the CEL and codes. Live logging caught it in the act.

 

[plain OM]

A quick reminder about my experience four years ago with this: I had a switch that measured around 20 ohms, but would miss the high pressure intermittently, enough to set the CEL and codes. Live logging caught it in the act.

I certainly remember that one.

I didn't mean to imply that the code is set only in one direction. It can happen when the system goes from low to high, but the pressure switch remains in the Low position, i.e., low resistance; or, when it switches from high to low, and because of bad contacts in the switch, the resistance doesn't drop from being an open circuit to being fairly low, like 20 Ohms. The 20 Ohms is an indicator, but the ECM appears to trigger the code when the resistance "doesn't cross" the 400 Ohm level. I've done the experiment in post #56 several times since, and it's 100% repeatable. It's a simulation, but a fairly simple one.

 

[OUTBACKZUM]

Code P0028 Driver side solenoid. I know this is an old post, posting for others who will come across this.
The solenoid on the driver side can be taken out without having to take out the Timing Belt assemblies.
There is a sensor next to the solenoid, all you have to do is loosen it, (not take it out). After that you should be able to take out the solenoid.

2010 Subaru Outback 2.5.
God Bless!

 

[bdp]

P0026 Code

Driver's side : 1.7 ohms
Passenger side: Open circuit

 

[turboisturbo]

2006 2.5L H4 ej253. Engine cold and not running.

I have a P0028 code coming on and off since a couple months. No effect on idling whatsoever, even after a code reset.
I checked the resistance today in both left (P0028) and right side (no code P0026).

Left (driver) side : wire is not original, it was soldered to the original wire. Looks brittle and cracked at the junction of the connector. It is still attached though but I will replace with hi-flex silicon wire. Inside the switch male connector, there was a fair amount of oil. It didn't leak out but the white connector was oily too. The resistance reading (same everytime) was around 1.5 ohm.

Right (passenger) side : Original wire and loom. No apparent oil inside. The resistance reading started at around 400 ohms, then every read was lesser until it top at around 46 ohms. I verified my ground connection multiple times and used the same for both switches. I also tried to move my test probe over the male connector to see if the connection was good. I don't have a P0026 code and never did.

The left switch connector wire seems like it can mess with the ECU. But does the resistance reading of 1.5 ohms indicated the switch is likely closed (short). The oil makes me think it should be replaced.

How come I have a high resistance reading on the right switch (46 ohms) and no CEL ? Should I replaced both?

 

[plain OM]

@turboisturbo

Just so that there isn't any confusion, industry standard is to identify "right" and "left" as when sitting in the car facing forward. Consequently, the "right" side is the passenger side in LHD vehicles, and the "left" side is the driver side.

The two codes P0026 and P0028 are side-specific. P0026 is for the right/passenger side, and P0028 is for the left/driver side.

Inside the switch male connector, there was a fair amount of oil. It didn't leak out but the white connector was oily too. The resistance reading (same everytime) was around 1.5 ohm.

The oil inside might be preventing the switch contacts from fully closing (going from open circuit to a low resistance like 1.5 Ohms) rapidly, and the reverse. (But showing 1.5 Ohms when tested later.) If the resistance doesn't change within seconds of the ECM commanding a change in the lift, the code is set. (See post #54 above and that poster's P0028 code, switch and solenoid check out OK | Subaru Outback Forums for one example.)

Because there is oil in the connector and, unless oil was spilled on it, the oil is coming up from inside. That means the switch itself is faulty (there shouldn't be oil inside) and should be replaced regardless.

How come I have a high resistance reading on the right switch (46 ohms) and no CEL ? Should I replaced both?

See post #56 above. (It appears the resistance would have to be higher than that to cause a code, but I would change the switch given that it starts at around 400 Ohms.)

NOTE: Observe the cautions posted in discussions here about switch replacement, namely, do not overtighten when installing the new one. (Search the forum for threads dealing with P0026 or P0028.) The area of the cylinder head where the switch is mounted is prone to cracking!

There is still the possibility while the switch needs to be replaced, there could be another reason for the P0028, including a faulty solenoid or clogged filter screen (avls filter and P0026 P0028 | Subaru Outback Forums ).

 

[turboisturbo]

@turboisturbo

Just so that there isn't any confusion, industry standard is to identify "right" and "left" as when sitting in the car facing forward. Consequently, the "right" side is the passenger side in LHD vehicles, and the "left" side is the driver side.

Sorry it always messes with my brain. I edited to avoid confusion.

I've read a couple of those threads, I understand there is irregularities in both. The left switch wire is definitely a cause for bad connection. The oil just shows the switch itself is dead or dying. I will replace both. I've seen how little the threads are on the switch. I'll be careful.

Thanks

 

[plain OM]

Please let us know what you do and how it turns out, or if there's more to be looked at. It will add to the knowledge base here and thereby help others.

 

[visitor]

@turboisturbo NOTE: Observe the cautions posted in discussions here about switch replacement, namely, do not overtighten when installing the new one. (Search the forum for threads dealing with P0026 or P0028.) The area of the cylinder head where the switch is mounted is prone to cracking!

FUEL INJECTION (FUEL SYSTEMS)(H6DO) > Variable Valve Lift Diagnosis Oil Pressure Switch
REMOVAL
...
2. Disconnect the ground cable from the battery.
...
4. Disconnect the connector from the variable valve lift diagnosis oil pressure switch.
5. Remove the variable valve lift diagnosis oil pressure switch.
INSTALLATION
Install in the reverse order of removal.
NOTE:
Apply liquid gasket to the variable valve lift diagnosis oil pressure switch threads.
Liquid gasket: THREE BOND 1324 (Part No. 004403042) or equivalent
Tightening torque: 17 N·m (1.7 kgf-m, 12.5 ft-lb)

 

[turboisturbo]

Please let us know what you do and how it turns out, or if there's more to be looked at. It will add to the knowledge base here and thereby help others.

The other day I replaced both oil pressure switch. I noticed the left one (driver side) is not OEM (black) and was leaking quite a bit. After removal, the resistance between threads and prong is 0.4 ohms, pretty much short.

The right one (passenger side) wasn't leaking and is identical to the OEM part (grey). After removal, the resistance between threads and prong is 45.8 ohms.

Another point goes to OEM parts!

I cleared CEL fault code and it didn't come back since two weeks ago. The car also feels like it runs smoother, but I also did an oil change and outside temperatures are getting warmer.

 

[willt629]

I had the p0026 code on a 07 forester so I replaced the bank 2 oil pressure switch and it left me with a p0083 which is Intake Valve Control Solenoid Circuit High (Bank 2). the new switch has a resistance of 1 ohm while the original switch on bank 1 is reading about 5 ohms. Im thinking that I should replace the new switch with on that has a little more resistance. My logic is that the low resistance of the switch is allowing too much voltage to flow through the circut but im not sure.

 

[plain OM]

I had the p0026 code on a 07 forester so I replaced the bank 2 oil pressure switch . . .

P0026 is for the Bank 1 side. Bank 1 is the right side, i.e., under the hood, the side of the engine closest to engine air filter and the ABS control unit. On the right side, the pressure switch and the solenoid are at the back of that head.

The P0083 applies to the oil switch solenoid on Bank 2, i.e., the driver side, closest to the battery. On the driver side, the pressure switch and the solenoid are at the front of that head.

The oil pressure switch would not cause an apparent fault with the solenoid. But if you were working around the Bank 2 pressure switch and solenoid, check the wiring to the solenoid, i.e., connector and wire leads, especially for breaks and or shorts to a ground or to other wires. Check that the connector at the solenoid is securely attached and not cracked or broken.

 

[willt629]

I have been at this problem for about a week now. this is really my first time dealing with electrical issues so I am likely making some stupid mistake. the way I tested that the connections were good is by using the E.C.M. plugs.
To test the oil switch I used the continuity setting on my multi-meter and went from connector B-134 pin 32 to engine ground which gave me about 1.4 ohms
To test the solenoid I went from connector B-137 pin 30 to pin 31 which gave me about 8.4 ohms I also tested between the two pins of the solenoid which gave me 7.6 ohms (which is in spec per the diag procedure) leaving about 0.8 ohms on the wires.
I have also manually actuated the solenoid while the car was running and was able to hear a difference in idle speed. I even hooked up the meter to the switch while I was doing that and was able to see the switch operate when I actuated the solenoid (going from about 150 ohms to O.L.). I also followed the diag procedure for testing for shorts on both the switch and the solenoid. I even took off the cam pulley and removed the holder to check for blockages but saw nothing.
I cant think of anything else that I can do and I may just admit defeat and take it in somewhere. any advice would be appreciated.

 

[willt629]

Engine Diagnostics (H4SO) - Google Drive

drive.google.com

if you go to diag procedure with dtc.pdf at the bottom pages 3 and 25 might be helpful