Car has 242K miles, stock, paper clip EGR off after CBU in 2018 at 175K miles.

The water pump went out last week. Before I replaced the water pump, I went ahead and replaced the boost hose. Battery was low but was able to bump the starter to get the stretch belt on the AC.

Got everything back together. charged the battery, bleed the cooling system using the bleeder on the tank, and ran it with cap off to ensure stead return flow to the tank.

I cleared the codes, and went to drive around the block. It went into Limp Mode and through a bunch of codes:

Central Control Unit Code
A2CB

Enginer Codes:
4CAE Position Sensor?
4BAD ?
4530 Charging Pressure Control
4592 Rough controler cylinder 4

Rain Module Codes
A669
A66E

P203B Reductant Level Sensor

Where do I start?

The one that sticks out to me is the 4530...underboost situation. Maybe check your new boost hose to make sure it didn't come undone, those retaining clips, with the angles and limited space can make it challenging to fully seat. Good luck...

Thanks, I will certainly check the boost hoses and inter cooler. It was a bit a struggle to get it in.

The cold side Boost hose was the problem a month ago at the track, the cold side hose clamp broke and the rubber to metal pipe separated.

A local BMW specialist is scratching his head, Vacuum confirmed at 26 inches. Hed wants to do exploratory surgery so he can physically check the turbo etc. at $,1000 to start..

At this point not sure the car is worth investing in. Any other way to diagnose Limp Mode?

He's a specialist and hasn't checked the $20 pressure convertor or vac lines that is most likely causing your issue?

Find someone else to look at the vehicle or DIY it. 4530 is a simple fix.

Also, Injector #4 is most likely going to need replacing.

He said the vac hoses look like crap but are holding 26 inches, so sounds like he checked for vacumm. I have converters and vac lines, but did not wnat to install until the car was stable after the water pump repair.

Will replace the converters and vac lines and see if the clears it up.

PCs and vac lines are maintenance items.

I replaced ALL of the vac lines and both converters today. Unfortunatley, that did not resolve the problem. The car went into limp mode within a few hunderd feet of the house.

I checked a few things before I got started:

1) The system is generating 29lbs of vacuum.
2) The high pressure turbo actuator pulled in as sson as the car started
3) The control valve located under the converter housing was holding vacuum.
4) The actuator under the EGR cooler was working and holding vacuum
5) The EGR controler was holding vacuum
6)With a mightyvac I was able pull over 20 inchs of vacuumm on the vacumm supply side, but it did not hold vacuum and slowly leaked down. Assuming the old vacuum lines may have been leaking or the line to the motor mount might be the cause? Did not change the vacuum line to the motor mount. I did replace both vac lines from the supply manifold under the intake to the converters.

All vac lines were replaced. I used OEM vac lines.

Any ideas on what to do and or check next?

Are you still getting 4530? Need the latest codes to figure out what's going on. If you are, watch this..



Did you also test the EV valve that connects to the compressor bypass? The bypass itself can get sticky, does it it move the entire range when vacuum is applied?