The BMW fault code 120408 technically stands for charging pressure control, deactivation: pressure build-up blocked. In most cases this indicates there's an issue with the boost pressure solenoid. The solenoid controls the pressure, in the intake of a turbocharged engine, delivered to the wastegate actuator, which controls the exhaust flow around the turbine. It works off of vacuum pressure and are easy to locate, follow a line from the vacuum pump. When it goes bad it will cause the car to go into limp mode. There are usually two solenoids on a BMW and You should replace both when one fails. They cost around $50 each. A repair shop will charge between $250 and $270 to change them.
Edward S
July 30, 2020
The code 120408 for the BMW means it's a problem with the charging pressure control, plausibility pressure being too high.
BMW316i, 2013 Error Code 130308, 120408. Hi All need your help to diagnose the issue. No warning lights on Dash but showing some error mentioned. This is the summary of the issue. Car hesitates while driving especially on hard acceleration. Switching from 1st to 3rd for example and when accelerating hard it hesitates during the start only, it looks like hesitation is coming underneath the gear. No difference in driving mode after this issue ( Comfort vs Sport) Car showing drive transmission error ever since the issue. Even after clutch replacement. Things that I replaced recently: Clutch, flywheen replacement, spark plug, air filter , oil filter clean, also mechanic said he cleaned fuel filter Mainly After clutch replacement I didn't have the hesitation issue, it sometimes showed up but very slightly in morning, but it got worse when I topped up 1 lt oil last week. All this hesitation issue got started when the mechanic did engine flush 1 year back. Please help as I spent a fortune money already and couldn't solve this issue.
I have same problem. I change the timing chain kits. Now it's OK n smooth
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