Subaru Outback Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
Hi and thanks ahead of time. My 2008 obw 2.5 sohc naturally aspirated is throwing a p0028 code and not allowing me to go past 4000rpms.

It's an automatic and the rpm issue occurs in Auto and sport mode. I recently had the engine out and did the head gaskets, valve covers. The timing belt was replaced recently but not by me (silly that I paid someone). Anyways I had the heads milled and they cleaned them while they were off. (I think they submerged them in some detergent and maybe gummed up the screen under the oil pressure switch in the process)

I pulled the variable valve timing selonid and cleaned, checked function on car battery, reinstalled but the code returned. I'm afraid the little screen under the oil pressure switch may be plugged as I didn't remove sensors before having the heads worked on And didn't check after.

Could these problems be related? Only the one code has come up. I was going to clean the mass airflow sensor, possibly pull the timing belt off and the camshaft pully on bank 2 to remove the part of the head where the seleniod and switch are found to inspect screen.

Other thoughts are to replace O2 sensor, Pcv valve to try and address rpm issue if it's not related.

Please help!
Jamie
 

·
Registered
Joined
·
18,421 Posts
There's lots of posts here about the P0028 code. The code applies to the variable valve lift system on the left (i.e., driver) side of the engine. There's a corresponding code, P0026, for the right side system.

Although the descriptions for these codes refer to a "solenoid", the problem is often the related oil pressure sensor switch.

Use the search function here for P0028. There's lots of threads/posts with details of what can be checked, and how to replace the oil pressure sensor switch (if necessary) without ruining the head. Look through the search results, and if there's still questions, post back here.
 

·
Registered
'18 OB 3.6R
Joined
·
64 Posts
A quick test of the solenoids would be to swap them left/right and see if the code follows to the other side. If it doesn't - then it's probably not the solenoid.
 

·
Registered
Joined
·
18,421 Posts
I'm not aware of any "failsafe", such as an rpm limit, applied when the code is registered. Also, I don't recall anyone mentioning a limit when the codes were present, but I might have missed it.

Are you noticing the 4000 rpm when driving or is that when parked and revving the engine in P or N?
 

·
Registered
Joined
·
4 Posts
Discussion Starter #6
It was while driving, although I didn't try while the car was in park. I think the 4000rpm limit was related to the p0028 code because the problem seems gone now that replacing the pressure switch seems to have fixed the issue and related CEL code. It also makes sense that the ecm would prevent over reving when there is an issue with valve timing at higher operating pressure. We will see... Thanks!
 

·
Registered
Joined
·
18,421 Posts
It was while driving, although I didn't try while the car was in park. I think the 4000rpm limit was related to the p0028 code because the problem seems gone now that replacing the pressure switch seems to have fixed the issue and related CEL code. It also makes sense that the ecm would prevent over reving when there is an issue with valve timing at higher operating pressure. We will see... Thanks!

Good to hear although I guess l have to revise my understanding of the impact of the code.

Did you replace the switch yourself, or have it done?

Genuine Subaru part, or other?

Incidentally, if that is a 4-cylinder 2.5 non-turbo, then it does not have variable valve timing; rather, it has variable valve lift, which is actually only two positions (low and high) for one of the two intake valves at each cylinder.
 
1 - 8 of 8 Posts
Top