P1557
Charge Pressure Positive Deviation.
- Volkswagen
- Powertrain
- Manufacturer code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 57
- FaultThe specific fault in that area
What it means
P1557 on Volkswagen group vehicles means Charge Pressure Positive Deviation. The engine control unit saw actual boost pressure rise above the specified target by more than the allowed margin for long enough to set the fault. This points to the boost control system not limiting pressure properly, and the exact components depend on the engine and turbo type.
Symptoms
- Engine warning light on, sometimes with the car going into limp mode
- Sudden surge or harsh power delivery under acceleration
- Power cut or reduced performance when boost is high
- Whistling, fluttering or blow-off noises from the turbo or intake
- Possible extra black smoke on diesel engines
- Occasional rough running or jerking under load
Possible causes
- Boost control (N75-type) solenoid faulty or its electrical connection poorlikely
- Wastegate or variable vane mechanism sticking, seized or carbon-fouled so it cannot reduce boostlikely
- Vacuum or pressure lines to the actuator split, loose, blocked or fitted wronglylikely
- Faulty vacuum or electric actuator that does not move to the commanded positionpossible
- Charge pressure sensor or intake air sensor reading incorrectly, so the control loop is working from bad datapossible
- Vacuum pump weak or failing, on engines where it supplies the actuatorpossible
- Outdated or faulty engine control unit software, where the manufacturer lists it as a known cause for the enginerare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting engine speed, load and temperature when the fault set
- Inspect the boost control solenoid wiring and connectors, and all vacuum and pressure hoses, for damage, looseness or incorrect routing
- With a scan tool, compare specified and actual charge pressure in live data during a road test and see when the overshoot occurs
- Command the boost control actuator in an output test, or move it by hand where the design allows, and check it moves freely through its full range and returns
- Check the charge pressure sensor reading against ambient pressure with the engine off and for plausibility under load
- Test the vacuum supply to the actuator and the vacuum pump output, if the engine uses one
- Inspect the turbo wastegate linkage or variable vane mechanism for sticking, play or carbon build-up
- Check the manufacturer's service information for software updates or known issues for that specific engine
How to fix
- Replace the boost control solenoid or repair its wiring and connector faults
- Replace split, blocked or wrongly routed vacuum and pressure lines
- Replace or recalibrate the actuator, following the manufacturer's procedure for the model
- Free or clean a sticking vane mechanism or wastegate linkage if serviceable, otherwise repair or replace the turbocharger
- Replace a faulty charge pressure sensor or a failing vacuum pump
- Apply an official software update only if the manufacturer lists it as the fix for this fault on that engine
Can I keep driving?
Medium severity
Short, gentle journeys are usually possible, but avoid heavy throttle because overboost can damage the turbo and engine. Get it checked soon, and stop driving if the power surges badly or the engine runs roughly.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.