2C57 Fault Code: Charge Pressure Too Low (BMW Repair Guide)
2C57 is a BMW-specific hex fault code meaning the DME could not reach its requested charge pressure. It usually comes from a boost leak, a stuck wastegate or a vacuum problem, and it often arrives together with limp mode.
— Tekin Code
2C57 is a code from BMW's hex fault code system, stored by the DME, and it means "charge pressure control, plausibility: pressure too low". In plain terms the DME asked for a certain amount of boost and the actual pressure measured by the MAP/TMAP sensor stayed clearly below that target. It is common on turbocharged engines such as N54, N55, N20/N26, N63, S55 and B48/B58. It will not destroy the engine instantly, but the car usually drops into limp mode, so severity is moderate to high — and behind it there is almost always a physical leak or a mechanical actuator problem.
What Does 2C57 Mean?
Based on pedal demand and its maps, the DME calculates a boost target and applies it through the wastegate or the VTG actuator. It reads actual pressure from the MAP sensor in the intake manifold. If the gap between target and actual exceeds a threshold for a defined period, the DME concludes the system cannot deliver the pressure it asked for and logs 2C57. This is not a sensor failure code; it is a control code telling you the system missed its performance target.
That is why 2C57 rarely appears alone — it is usually part of a chain. Seeing 3100 (boost pressure control deactivated) next to it is very common; 3100 is the consequence, 2C57 is closer to the cause. If sensor codes such as 2ABC are also present, deal with those first, because a bad sensor signal can lead the DME to the wrong conclusion.
Code .............. 2C57
Definition ........ Charge pressure control, plausibility: pressure too low
Module ............ DME (Engine Control Unit)
Related codes ..... 3100 (boost control deactivated), 2ABC (pressure sensor electrical),
30FE (overboost - the opposite direction)
Severity .......... Moderate to high - limp mode, power loss
Common engines .... N54, N55, N20/N26, N63, S55, B48/B58
Symptoms
• Obvious power loss — the car pulls as if it had become naturally aspirated.
• Limp mode, usually triggered during hard acceleration or on an incline.
• Check Engine light on; some cars also show a "Drivetrain" warning.
• Stumbling at high RPM, boost suddenly cutting out and then returning.
• Whistling, hissing or air-leak noise from the turbo area, especially at full throttle.
• Higher fuel consumption and lazy throttle response.
• The fault appearing more often in cold weather or after rain, as plastic parts contract.
Possible Causes
• Cracked charge pipe or a dislodged O-ring — the plastic charge pipe on N54/N55 is the classic 2C57 cause. Most common by far.
• Loose intercooler hose clamps or a split silicone/rubber coupler.
• Seized wastegate actuator or VTG mechanism, or a rattling wastegate rod with excessive play.
• Blocked or electrically failed boost control solenoid (PWM valve).
• Vacuum line leak, cracked hose, or a failing vacuum pump on vacuum-actuated systems.
• Torn diverter/blow-off valve diaphragm (the DV on N54) staying permanently open.
• Contaminated or drifted MAP/TMAP sensor reading actual pressure lower than it really is.
• Clogged air filter, crushed intake duct, or a restriction on the exhaust side (catalyst/DPF).
• Mechanical turbocharger failure — bearing wear, wheel damage, excessive shaft play.
• Aggressive or mismatched software (tune) demanding more boost than the hardware can deliver.
Diagnostic Steps with OBDThink
The only correct approach for 2C57 is to watch target and actual boost side by side. The RPM and load at which the deviation starts tells you directly whether you are chasing a leak or an actuator.
• 1. Scan all modules and map the code chain: if 3100 sits next to 2C57, note the order; if sensor codes such as 2ABC are present, address those first.
• 2. Read the freeze frame: RPM, engine load, pedal position and air temperature at the moment of the fault give you the scenario. Does it only happen at full throttle, or at part load too?
• 3. Plot target and actual charge pressure on the same live graph. Hitting target at low RPM and losing it higher up points to a leak; missing target everywhere points to the actuator or wastegate.
• 4. Watch the wastegate duty cycle: if duty is pinned at 90–100% because the DME cannot catch the target, the control system is doing all it can and the problem is mechanical.
• 5. Compare ambient pressure and MAP with the ignition on and the engine off: both should read around 1.00 bar. A gap between them means the MAP sensor has drifted.
• 6. Run a leak test: pressurise the charge air system (boost leak test) or use smoke to check the charge pipe, intercooler and couplers.
• 7. Verify the vacuum side: measure vacuum at the wastegate actuator, command the solenoid in an activation test, and inspect hose ends for cracks.
• 8. Don't forget the exhaust: a clogged catalyst or DPF also prevents boost from reaching target — evaluate exhaust back pressure.
Reference values (vary by engine and calibration)
Ignition on, engine off:
MAP (absolute) ....... ~1.00 bar (should equal ambient pressure)
Idle (engine warm):
MAP (absolute) ....... 0.35 - 0.45 bar
Wastegate duty ....... low / control inactive
Full throttle (WOT), mid RPM:
Boost target ......... 1.7 - 2.1 bar absolute (roughly +0.7 ... +1.1 bar gauge)
Boost actual ......... deviation from target should stay < 0.15 bar
Wastegate duty ....... dynamic, 40% - 80%
EXAMPLE OF A FAULT:
Target 1.95 bar / actual 1.35 bar, duty 100% -> leak or seized wastegate
Hits target but drops off at 5000 RPM -> charge pipe / coupler leak
Log the target/actual boost pair with OBDThink during a short full-throttle pull. The RPM at which the deviation begins tells you far more about the size of the leak than staring at idle values in a workshop.
The Fix
Work from the most likely to the most expensive, guided by the data. Replacing the turbocharger straight away is unnecessary spending in the large majority of 2C57 cases.
• Charge pipe and O-ring: if cracked, fit the aluminium replacement and renew the O-ring every time it comes apart. Low cost and the most frequent fix.
• Intercooler couplers and clamps: replace split hoses and torque the clamps properly. Low cost.
• Boost control solenoid: replace if it fails an electrical or activation test. Low to moderate cost.
• Vacuum hoses and connectors: renew hardened, cracked lines as a set. Low cost.
• Wastegate actuator / VTG mechanism: adjust and free off if sticking, replace the actuator if damaged. Moderate to high cost.
• Diverter valves: replace as a pair when a diaphragm has torn. Low to moderate cost.
• MAP/TMAP sensor: replace if it deviates from ambient with the ignition on. Low cost.
• Exhaust restriction: a blocked catalyst or DPF needs cleaning or replacement. High cost.
• Turbocharger: overhaul or replace once shaft play, oil leakage or wheel damage is confirmed. High cost.
Some engines need the wastegate adaptation / control values reset after the repair. If you replaced a part and the code still returns, check whether the adaptation was performed before you start suspecting mechanical failure.
Can You Still Drive With This Code?
If the car drops into limp mode you will experience sudden power loss in traffic, which is a genuine risk when changing lanes or overtaking. A short, careful drive to the workshop is acceptable, but avoid full throttle, heavy loads and long trips. If the cause is mechanical turbo damage rather than a leak, continuing to drive will make it worse.
Clearing the code does not restore boost; it only removes limp mode temporarily, and the fault returns on the first full-throttle pull. The right approach is: repair the leak or the actuator, clear the fault memory with OBDThink, then watch the target/actual boost pair again during a short load test. If the deviation stays under 0.15 bar and the code does not return over several drive cycles, the job is done.