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The BMW fault code 120408 typically refers to an issue with the boost pressure solenoid, which is responsible for regulating the pressure in the intake of a turbocharged engine that is delivered to the wastegate actuator. When this solenoid malfunctions, it can cause the car to go into limp mode. To fix this, it is recommended to replace both solenoids, which cost around $50 each. A repair shop will typically charge between $250 and $270 to replace them. You can easily locate the solenoids by following a line from the vacuum pump.
In BMW terms, the code 120408 indicates an issue with the charging pressure control, where the pressure is deemed excessively high based on plausibility.
I'm receiving an error code related to the boost pressure control on my n63, causing a shutdown due to blocked pressure build up. I am planning to replace the boost solenoid in hopes that it resolves the issue.
Here is a paraphrased version with a unique twist: "December 4th, 2008
I saw a notification about timing chain problems on my M4.
I apologize for letting you know that the solution attempted was unsuccessful. I am unsure of the next course of action to take at this point.
The timing chain requires replacement in the vehicle.
BMW316i, 2013 with Error Codes 130308 and 120408. Seeking assistance to diagnose a problem — no warning lights on the dashboard, but errors reported. The issue summarized: car hesitates during hard acceleration, especially when shifting from 1st to 3rd gear. The hesitation seems to originate from beneath the gear. No change in driving mode effectiveness (Comfort vs. Sport) after issue occurred. Continuously displaying a drive transmission error. Despite recent clutch replacement and other maintenance (flywheel, spark plug, air filter, oil filter, fuel filter cleaning), hesitation persists. Originally noticed after an engine flush a year ago, exacerbated after adding oil. Seeking help after already investing a significant amount of money without resolving the problem.
I encountered a similar issue but resolved it by replacing the timing chain kits. Everything is running smoothly now.
Only appear when the engine is warmed up.