Stevo F Posted September 21, 2020 Share Posted September 21, 2020 Not sure if these two codes are related or a coincidence. We've owned our 2008 Forester since last year and recently started getting CELs for first P0171, I did a couple of ECU resets, then we got both the P00171 and P0028 codes. For the P0171, my mechanic advised it's most likely a vacuum leak but I didn't find anything obvious wrong, so not sure where to proceed from there. For the P0028, I've read this is Intake valve control solenoid circuit. I'll start with the obvious- clean the connectors for the solenoid and the oil pressure switch. Also the oil level is fine and the oil is clean. If the cleaning doesn't work, would it make sense to replace the oil pressure switch since it is an inexpensive part? Since the cheapest OEM solenoid is nearly $100, I don't want to put money into replacing it until I've been able to test it or rule out other issues. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 21, 2020 Share Posted September 21, 2020 (edited) You have a vacuum leak or a bad MAF/O2 and a bad AVLS pressure switch (not the solenoid). Replace them both they are prone to failure. Clean the MAF (you have to scrape the elements), and check the fuel trims. GD Edited September 21, 2020 by GeneralDisorder Quote Link to comment Share on other sites More sharing options...
Stevo F Posted September 21, 2020 Author Share Posted September 21, 2020 14 hours ago, GeneralDisorder said: You have a vacuum leak or a bad MAF/O2 and a bad AVLS pressure switch (not the solenoid). Replace them both they are prone to failure. Clean the MAF (you have to scrape the elements), and check the fuel trims. GD Thank you. The car otherwise runs fine so for the P0028 I suspect the switch or solenoid is at fault, vs. an actual VVT issue. So you are referring to the oil pressure switch that sits next to the solenoid and recommend replacing them both? For the P0171, I do have some MAF cleaner so I will try that. I assume the MAF on this model is located between the the air box and intake duct (like it is on my '98 Legacy with MAF). Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 21, 2020 Share Posted September 21, 2020 Yes the switches are bad. They often leak from the electrical connector. Replace both as they can fail and leak an alarming amount of oil in a short time. And it's not VVT. It's VVL. MAF cleaner isn't necessary. I use brake cleaner all the time. But you need to scrape the elements with a pocket screwdriver. And sometimes they still need to be replaced. Check your live data MAF grams/second - should be around 3.2 at idle. GD Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.