P0234 over boost code intermittently at full throttle, boost surge in midrange and half throttle

Abe Technician Minnesota Posted   Latest   Edited  
2011 Cadillac SRX Premium 2.8L (6 LAU) 6-spd (6T70)
P0234 — Turbocharger/Supercharger "A" Overboost Condition
Boost Surge In Midrange At Moderate Throttle

First post here, thanks in advance for your time. Been a while since I had a car I couldn't figure out. Anyway, best I can tell this is an engine shared with Saab? Also, herd Holden designed? Anyway, way way way to much mis-information from all data and Identifix. Also, my modis ultra and zues are giving me erroneous data info compared to autel. First time seeing this on a gm vehicle. Just to start, map sensor is combined with intake temp. sensor as best I can tell. temp sensor seems to be working properly. with snap on scanner map is high in data, key on engine off. autel matches baro. but reads 15 psi key on engine off. ended up putting manual gauges inline before and after the turbo wastegate solenoid valve. max boost reached multilple times on road test was 16 psi. The other gauge was to measure what the waste gate actuator was actually getting. ironically, on that road test the code for over boost didn't happen, but was able to see a fluctuation out of the wastegate solenoid valve when part throttle turbo surge was happening. I am at a loss... any body have ideas? 

James Owner/Technician
James Default

I could be wrong, but I think those use the same boost control solenoid that Volvo has used for quite a while, at least through the 00's. They get sticky and slow reacting, and can cause a surging condition under boost, since the valve doesn't keep up with the duty cycle commanded,

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Ray Diagnostician
Ray Default

I had a 4 cyl Ford with the P0234 and the wastegate solenoid tested ok, but a new solenoid fixed it.

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Eric Owner/Technician
Eric Default

Do you have bi-directional controls to use for testing as asked for in the SI? I had no problem finding the testing procedures for this problem in Identifix. They have a good OEM procedure shown there. You need a good compatible scan tool to test for this code otherwise you will be doing a lot of guessing. All the ones I've worked on have had issues with the waste gate control system. Using…

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Tanner Instructor
South Carolina
Tanner Default

Anytime there is an over boost condition there are a couple tests I like to see performed. The first is you need to graph boost pressure and map sensor from key on engine off, idle and then on a cruise reaching wide open throttle for a few seconds. I prefer to graph merge this data so I can see the two graphs on top of each other. The reason for this is to make sure the sensors are reading…

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