I have a 2008 MCS with 71K miles. Lately, I've been getting the half engine warning light on the tach, but no check engine light. The CCID code is 117. Usually happens when I step on the gas hard and get boost. Sometimes it goes away and once I step back up on the gas I get the warning light. I don't feel the engine in limp mode at all. sometimes I might get a misfire code (273E, 273D, 2775, 276A), but after clearing the codes they go away but 28AA keeps popping back up.

I've heard that it could be the diverter solenoid valve or the High Pressure Fuel Pump. How can I correctly diagnose which is it? Last year all spark plugs and coils were replaced, as well as the turbo oil return lines, and the thermostat housing.

I also get error code A127 on CAS. Haven't been able to find what that is. I have an old USB K-DCAN cable from my NCS Expert days, that I've been using with some apps (Bimmer-Tool lite) to read the codes.

 

Google claims 28AA is a failed diverter valve, seems like replacing that is your best bet. Bad DV is also consistent with symptoms.

Don't have too much faith in new coils - I replaced the OE set with a Delphi set on a 2007- it took about six months for 3 of the new coils to go TU. Replaced the Delphis with a Bosch set, three years later all is well.

A127 - Incorrect signal from engine management - Is all I could find - no idea what it could mean.

 

I thought Delphi was good. That's the same I got.
Is it worth getting the diverter with Alta stiffer spring? Should I go for OEM or after market is fine?

 

28AA is deviation of boost pressure upstream of throttle valve too far from target pressure. Deviation limit is 100 mbar on factory software. Any changes to turbo or tuning? If not I'd look at the diverter valve first. Remove it, make sure it moves freely and the rubber isn't torn. An open or short inside the DV valve itself will trigger a different error code on power up. The newest style factory diverter valve without the rubber diaphragm holds up to 25 psi of boost very well.

 

A BOV adapter spacer was was installed about a year ago as well. Could that be the culprit?
haven't had a chance to check the diverter, yet.

 

It is another possible leak source so I would recommend removing it while troubleshooting. You can always re-install it later once you resolve the root cause.

 

Why so much staining on coils 2 & 4? Coolant leak?

 

Not sure why. I did clean the engine bay a few weeks ago (the problem started way before that).

 

I went for a long drive yesterday 70 miles and noticed that I was in fact in limp mode. Only 3 PSI at most of boost. If I went hard on the gas it would go away and get full boost, but immediately get the half engine check light again and if I boost it only get 1 or 2 PSI.

I got the new diverter valve and installed it, but still no boost. Strange thing is that I get no engine check light at all after driving a few miles. I connected with Bimmer-Tools and now I get the error code 28B1. I've cleared the codes a few times. I do have a cheap diverter adapter, but can't find the shorter screws to test without it.

 

Pull the vacuum line off the vacuum pump and see if it makes a hiss, like it's releasing pressure. Then take a vacuum gun and plug up to the hose you just removed and pump. It should hold 10 psi with no deviation. If it doesn't hold, then your Boost Solenoid is worn out and needs replacing. it's located under the intake manifold and has two rubber/rigid hoses connected to it. I've found that most of my rebuilds have needed a new solenoid. The internals wear out and no longer holds the one-way pressure.

 

I had plugged the diverter valve electrical connection backwards. I plugged it back correctly and now I'm getting code 2885. Boost will not go over 3 PSI. I checked the vacuum line from the wastegate actuator and it seemed fine. I plugged my vacuum cleaner, since I don't have a vacuum guage, into the hole and it pulls the rod closing the wastegate.
I'm tempted to change the pressure solenoid, but am afraid that it still be something else. Kinda hate having to throw money into it trying to diagnose what's wrong.

 

https://www.google.com/search?q=p288...obile&ie=UTF-8

check your hoses might have a boost leak.

 

1) A vacuum line gone soft (which they do as they age) won't be readily detectable by inspection and can collapse under vacuum. Suggest you replace the vacuum lines as material is cheap (~80 cents a foot)
2) It appears that you still have the OE pressure converter, suggest replacing it. If you want to try to debug it, connect a vacuum gauge to WG actuator line while driving. My money is on a bad pressure converter.

 

I'll probably buy a new Pressure converter (11657599547). What is the size of the vacuum line that I should purchase? The OEM lines are about $100, for what it is ill probably get like 10 feet or so of regular rubber hose lines. Wish I had a vacuum guage to test.

 

I can't recall the sizes - there are two. Keep in mind that there are pieces of rigid nylon pipe in between the rubber bits, the nylon generally does not need to be replaced.

google the part number for the OEM hose kit - you'll find it for around 60 or so, including shipping (11657593718)
re: 11657599547 - The Pierburg brand will be around half the cost of the Mini part...jus' say'in .....

The pressure converter has a large and small nipple for the large and small vac line.....

 

Similar thing happened to me, turned out to be coils, although you mentioned you had recently replaced them.

 

I realized I have an aftermarket boost guage that measures pressure and vacuum. So, I decided to connect to use a T fitting and connect to the waste gate line. It wasn't reading anything at all. I blew into the waste gate rubber hose and it is escaping air. I can't make it out where, but sounds from below the intake. I still haven't gone under the car to check. I pulled out the braided plastic weaving and the rubber hose and it feels rough and is sticky. I hope it is the hose that has a slit somewhere and not the vacuum tank. I'm waiting for the OEM vacuum hoses to arrive.

.

 

Found the problem.

Got under the car and found both vacuum tank lines disconnected. I cannot find a way to connect them back. It's very uncomfortable and can't find a position. Also only doing it with one hand....

Does it matter which vacuum line goes to the tank?

 

Connected the loose vacuum lines to the vacuum tank and finally got back max 16PSI back. No error messages. Drive about 10 miles. It had like an inch of vacuum line that connected from the line to the tank that was so loose it fell on my face. Cut a piece of 5/32 line that I had and after a bit of swearing and scraping my arms got in both ends.

 

I wish I had seen this video sooner.
My back is so sore. LOL.

 

Lou:
I found your post on the code 28AA. May i call you and ask some questions? I rebuilt the entire engine in my ‘07 S. I’m not showing boost on my gauge. I asked the dealer to report any suspicious codes while they were re-doing my alignment and tightening all the suspension parts they neglected on the first try.
I invested in a Turbosmart Kompact plumb back electrical. I installed it with a new turbo cartridge and actuator. I contacted turbosmart and the only thing they could do was send me a repair kit and offer to check the valve if i want them to do that. I checked the resistance and its within spec @ 36 ohms.
What do you think?

 

Sure thing. Since your getting zero boost the first thing I would do it remove the heatshield and look at the wastegate with engine off. Have someone start the car and you should see it close then open as I recall. If it doesn't close I would investigate the vacuum line plumbing to the pneumatic valve.

 

The waste gate closes on start. I set the waste gate without the engine running and about 10-12 in hg on the waste gate at the closed position. So the actuator moves about 10-12 mm to close on start.

Vacuum line are new an i checked to make sure the bigger port is connected to the actuator, small port to the tank and vacuum pump to the tank. The car runs good, just no boost above atmosphere.

Let me know when you are available and a number to call.

Thanks Lou.

 

I should have a little free time around 3:15 or 3:30 EST if that works for you.
Contact info

 

Pull vacuum on the waste gate and see if it holds. Every one of the 10 R56 I've rebuilt have leaky wastegate. Even the slightest leak will be detected by the system after a short drive and drop it into limp mode. It should hold solid.