Hi I have a bone stock 2009 JCW hardtop with 80k miles on it. I got it a month ago and the horns don’t work, so I decided to upgrade them to Hella twin trumpets. I installed them last weekend (new wiring w/relay triggered off of positive wire from old horns). Since then, the car runs and drives perfectly if I stay out of boost, but if I get it over 3-4psi, it goes into reduced power mode AFTER I let off the gas... I can floor it in 6th gear and run it up well over 100mph without any issue, but as soon as I let off, it goes into limp mode. I have ISTA and saw that it throws codes 2B0B and 2B06 (throttle valve potentiometer 2). If I reset the throttle adaptations, it runs normally again as long as it’s not in boost. One time it did throw a CEL with codes P0120 and P0222. My first thought was the throttle body, but my friend had a used one that I tried, but it still did the same thing, so I ordered a brand new OE throttle body, but it didn’t solve anything either. Since putting it in, the codes have changed to 2B0B and 2B02 (throttle valve potentiometer 1). I’ve tried completely disconnecting all of the wiring for the new horns and replaced the valve cover, since the dealership said my crankcase pressure was high 2 weeks ago when they put in a new HPFP. The battery is 2 years old and is pretty weak, so I’m going to take it to be tested tomorrow since it’s under warranty. Has anyone dealt with this issue before? If the battery isn’t the issue, the only other thing I can think to do is start checking the engine harness for power/ground and shorts, but I’d really like to not have to do that if someone has an idea as to what’s going on. Thanks!

 

Update: I got a new battery and registered it but the problem remains

 

Update 2: I replaced the charge pressure/temperature sensor but the issue continues as before. There also was an inactive MAF plausibility code in the computer a few days ago but hasn’t come back, so I’m beginning to think it’s either a wiring or DME issue. Any thoughts on where to start testing the harness?

 

Since you've problems after getting in boost, have you checked the turbo and connecting parts to the turbo for faults?

Try cleaning the MAP/MAF sensor with the correct cleaning product.

Condition of the diverter valve.

Valve cover and the PCV hose.

Check for carbon buildup.

Timing chain.

 

I'm going to get this thread started again as I am having about exactly the same problem with a 2010 S with 74000 miles. The only difference is it happens for me as I start to lightly get into boost, not really after backing off the throttle. If I go 100% throttle it does not happen most of the time, even after I back off. I have been struggling with this about a month, and am on my second code reader (NT510 now) trying to find clues. i am getting the same codes as OP.

I had changed the diverter valve and it continues.
I changed the throttle pedal which has the sensors integrated into it.
New sparkplugs and coil packs about 3 months ago, before this happened but this issue did not start right after that change out.
Valve cover was changed less than two years ago.
Never had carbon cleaning done, but have not had any issues with it either. I run BG44 through the gas once in a while, Techron about every other tank.

Thanks for any more clues.

 

Try monitoring the short term fuel trim and long term fuel trim and see what kind of results you get.

 

What codes are you getting now? I would look towards the turbo. Check the diverter diaphragm. When my wastegate wasn’t closing properly I had issues under low boost like that, but not full boost. Usually under a slight load, it would go into limp mode. It was calling for boost, but not seeing the amount called for

 

Thanks for the help!
i have a Foxwell scan tool, what should I be looking for with the fuel trim levels?

 

These are what consistently comes up from the light boost trip into limp mode. I changed the DV, the rubber piece inside looked ok though but still put a new one in there. Sounds like I have what you had - mahalo for the help!

 

Fuel trim was to check to see if your engine is running correctly,

https://www.autoequipment.com.au/ima...iagnostics.pdf

Try this

https://cartechnology.co.uk/showthread.php?tid=9264

 

Well hopefully you will get it figured out. Some of the symptoms certainly sound familiar, lol. But those are not codes I’ve run into before. I was getting the typical boost plausibility error DTC’s related to boost pressure. It probably worth it to eliminate it from the list of possibilities though. If you don’t have a boost gauge, you can use that Foxwell scan tool to monitor live data and view boost pressure that way. Just a few easy things to do to see if maybe it’s an issue, is driving it while monitoring or recording the data. If it’s consistent enough of an issue, you may already know a certain part of the road or highway that it happens on or at often. Like an incline on the freeway, for instance.
For example, there was a sort of long inclined stretch of the freeway, where it would trigger limp mode almost every time I tried to accelerate just a little to maintain speed. Every. Single. Time. The only thing that kept it from happening was to manually downshift (auto trans) just before the hill. Increasing the rpm’s and motoring on like a champ was the only way to prevent it.
You can monitor data, to see what it tells you about boost, fuel trim, etc. The only real ways to check the wastegate itself is to look at it with a borescope, or pull the downpipe off the turbo and inspect it. You can use a vacuum pump to test the actuator and watch how it’s closing. It should pull shut at about 15 inches of mercury. If it’s loose or not sealing good and tight, it will probably need to be replaced eventually, usually the whole turbo.
Please remember, this is only my personal experience with the symptoms, and very well may be something else entirely. I’m just putting it out there to you, in an effort to help eliminate possible causes. There are many smarter and more experienced minds here than me! Lol..... But hopefully it’s helpful in some way.