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Old 11-29-2012, 09:15 PM   #1 (permalink)
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Default Check engine light - P0028 code

I've got a 2008 Outback 2.5 that just turned 50,000 miles. The wife is 300 miles from home and calls to say that the check engine light came on and the cruise control indicator is flashing otherwise the car seems to be running fine. Just had the oil changed last month and have had no issues with the car so far.

I found a procedure to get the engine code and had her go through the steps and it's showing a P0028 code - Intake Valve Control Solenoid Circuit Range/Performance Bank 2

I'm concerned about her getting stuck somewhere - we've got a major storm coming in tonight. Is this something that she needs to take in to a shop right away?
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Old 11-29-2012, 09:41 PM   #2 (permalink)
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Have her check the oil level. If its low, fill it, then find out why its low. If its not low, then there may be an issue with the control solenoid, pressure switch or oil circulation for cam lift to take place.

The VVL solenoid controls oil flow to change the camshaft lift. If its low of oil, the solenoid operates but the cam doesn't change and the pressure switch feedback doesn't change. Since the ECM only sees voltage data and not mechanical, it sets a code for the solenoid circuit assuming that the oil is at the proper level and viscosity and the signal returned to it by the pressure switch is correct.

There is not a "fail safe" operation enabled, but if it is due to low oil, it wouldn't be a good idea to drive it until the oil is full and the engine checked for a leak.
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Old 11-29-2012, 09:51 PM   #3 (permalink)
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Have her check the oil level. If its low, fill it, then find out why its low. If its not low, then there may be an issue with the control solenoid, pressure switch or oil circulation for cam lift to take place.

Oil level is normal and oil is clean
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Old 11-29-2012, 09:57 PM   #4 (permalink)
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Was an oil change performed recently? if so, what filter was used? I got this code shortly after an oil change (a couple of days) when I used a Walmart filter in a pinch. Changed out to a Purolator and haven't had it come back. But Cardoc's advice is first on the list. Especially looking for leaks around the solenoid housings. There was a post a while back where an '07 was missing a gasket from the factory. The resulting oil leak popped the code.
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Old 11-29-2012, 11:31 PM   #5 (permalink)
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Was an oil change performed recently? if so, what filter was used?

Oil was changed last month by my regular mechanic (been using him for the past 8 years) - not sure what filter was used but my Outback has had it's oil changed every 3-5k miles and doesn't burn a drop between changes.

What I'm really worried about is if the car is safe to drive. My wife is currently 300 miles away at a motel and we're debating having the car towed back home for $800
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Old 11-29-2012, 11:53 PM   #6 (permalink)
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I know it's risky making suggestions about someone's loved ones having car trouble out of town but, I THINK, if I were in your place, I'd collect phone numbers of dealers and car rental places along her route, clear the code if possible, and have her drive back. The car seemed to drive well anyway, and, even if it went into 'limp' mode, she could still get safely off the road. Just have her prepped to make a call and have the car towed. Don't be concerned about the disabled cruise or any disabled traction control. On newer cars, even a 'minor' trouble code is programmed to disable cruise and traction control so, it isn't unusual to have a CEL and 2-3 other lights on.

I have had spurious codes set in both my soobs. One was related to a bad cell in the battery. The other is still a mystery. It was tumble generator valve related in my WRX. even put the car in limp mode. cleared and never came back.

NO ONE could fault you for putting your wife in a rental and towing the car.

w'ever you decide, good luck.
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Old 11-30-2012, 08:27 AM   #7 (permalink)
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Oil level and leaks around the variable valve lift solenoids or pressure sensor switches have been seen before as causes of the P0028 code, as has been noted above.

The code is for bank 2. The related solenoid and switch are at the front of the left side head and easily checked for oil leaks. There's photos in this post: Variable Valve Lift oil pressure switch resistance

If there is oil around the pressure switch, it could mean that the switch isn't functioning properly although the variable valve lift is actually working. In the linked thread, I'm addressing the possibility that a P0028 code could also be generated by a poor contact inside the switch. It might be something to check when the car is being serviced.

If the oil level is definitely okay, and there are no leaks, it should be possible to drive home. Worst case the variable valve lift might not be functioning and this could affect fuel economy, and possibly emissions. But as cardoc noted, there's no "failsafe". As long as the check engine light isn't flashing, it's safe to drive the car. (I believe this is actually mentioned in the Owners Manual.)

I might not push the car at high speed for an extended period, and might opt to take slower secondary roads rather than interstates. This would avoid running the engine steadily at higher rpms which is where the higher mode of the variable valve lift is normally activated.

Hope you'll let us know how it turns out.
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Old 11-30-2012, 07:21 PM   #8 (permalink)
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She made it home with the car today and said it seemed to run ok. I didn't see any leaks around the VVL solenoid and the connections seemed to be good. Oil level is full and looks clean. I disconnected the battery for about an hour and then reconnected and took the car for a 5 mile drive - the check engine light stayed off but the car seemed to idle a little low and stumble when at a stop.

The dealer cant get me in until next Wednesday - wondering if it''s going to be ok to drive the car around locally until then
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Old 11-30-2012, 07:43 PM   #9 (permalink)
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Probably, but I must ask why disconnect the battery? To clear the CEL?

As the car seemed to be running well enough, the only apparent "problem" is the light being on, and the fact that the cruise control is disabled when the CEL is on.

In this regard, if in the next three drive cycles no faults had been detected (e.g. if the P0028 was a single "event"), the CEL would have gone out on its own and the cruise control restored, while the trouble code itself would have remained in memory for up to 40 drive cycles. This might have been useful for the dealer. Without any codes, the dealer might not have anything to go on.

Is your car still under the power train warranty (5/60k)? If so, then you would want the code(s) there so that it can be recorded on the work order. That way, even if the dealer doesn't find anything, at least there's a "history"; if it happens again slightly after the warranty is past, there might be a case for warranty coverage.

As for the rough idle, when the battery is disconnected, in addition to the trouble codes being erased, the "learned operation" of the ECM and TCM is also erased. (The ECM and TCM monitor how the car is driven and adjust various functions to best meet the driving needs while optimizing fuel consumption and emissions.) When the learned behavior is erased, the controls return to defaults, and it then takes some time to "relearn". There have been reports of "different" or unusual idling in these cases, until a few drive cycles have been completed. (The recommended method to erase codes is to use a code reader/scanner that has this capability. This way, only the stored codes are erased, but the learned operation is retained.)

Perhaps the code and CEL will reappear. If so, leave it for the service department to deal with.
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Old 11-30-2012, 08:49 PM   #10 (permalink)
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Just to add in to PlainOM's post, the computer also stores what is referred to as "freeze frame data". This is the data recorded from various sensors on the car at the time the error occurred. In removing the current flow from the ECM, the freeze frame is lost. It could have indicated the source of the problem.

You may also want to check the battery. If its original, it may be due for replacement and a weak battery will effect the programming and functions of the actuators and sensors on the engine and transmission.
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