What Does P1557 Mean?
The actual boost pressure is significantly higher than the target boost pressure commanded by the ECM (positive deviation). This indicates the boost control system is unable to properly regulate turbocharger output.
Safety Warning
Avoid aggressive acceleration and high load conditions. Overboost can cause catastrophic engine damage including detonation, head gasket failure, or internal component failure.
Common Causes
35%
Stuck or binding wastegate valve not opening properly
30%
Failed boost control solenoid valve stuck closed
20%
Vacuum leak in wastegate actuator control line
10%
Mechanical failure of wastegate actuator diaphragm
5%
Carbon buildup preventing wastegate from opening
Diagnostic Steps
1
Step 1: Monitor target vs actual boost pressure in live data during acceleration; note deviation amount
2
Step 2: Test wastegate actuator with hand vacuum pump; verify it holds vacuum and operates smoothly through full range
3
Step 3: Inspect wastegate linkage for proper connection, binding, or damage
4
Step 4: Test boost control solenoid with scan tool active tests; listen for clicking and verify vacuum output changes
5
Step 5: Inspect turbocharger wastegate valve for carbon buildup, damage, or restricted movement
Estimated Repair Cost
$200 - $1,500
Parts + labor, varies by vehicle and location
The actual boost pressure is significantly higher than the target boost pressure commanded by the ECM (positive deviation). This indicates the boost control system is unable to properly regulate turbocharger output.
The most common cause of P1557 (Charge Pressure Contr. Positive Deviation) is: Stuck or binding wastegate valve not opening properly
Typical repair costs for P1557 range from $200 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Avoid aggressive acceleration and high load conditions. Overboost can cause catastrophic engine damage including detonation, head gasket failure, or internal component failure.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1557 to identify the root cause.
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