The P1557 (17965) code means:

👉 Charge Pressure Control: Positive Deviation

On Audi/VW applications, 17964 / P1556 is defined as “Charge Pressure Control: Negative Deviation.” In plain English, the ECU requested more boost than the turbo system actually delivered. Ross-Tech lists the main symptoms as reduced power output and limp mode. Possible causes include boost pressure too low, hoses/pipes incorrectly connected, disconnected or leaking, charge pressure control defective, turbocharger defective, wastegate/regulating valve problems, and on some applications MAF-related issues.

👉 BSD = Bit Serial Data bus

This is a communication line used by BMW DME (engine ECU) to control and monitor key components.

2E7C is a BSD data bus communication fault. On BMWs that use the BSD bus, the DME communicates with several “smart” components over that single line, and when communication on that line breaks down, the DME can store 2E7C. BMW-focused diagnostic sources repeatedly identify the BSD participants as the IBS (Intelligent Battery Sensor), alternator/voltage regulator, electric coolant pump, and oil level/condition sensor.

The BMW 2E8B code indicates:

👉 Loss of communication with the IBS (Intelligent Battery Sensor)

The BMW 2DEC code indicates:

👉 A power management / battery monitoring fault

The BMW 2A99 code indicates:

👉 A correlation error between the crankshaft and EXHAUST camshaft

The BMW 2A98 code indicates:

👉 A correlation error between the crankshaft and intake camshaft

The BMW 29F1 code means:

👉 The fuel pressure is not plausible (not matching expected values)

The BMW 30FF fault code usually means “turbocharger, charge-air pressure too low” or underboost. In plain English, the engine computer requested more boost than the turbo system actually produced. On BMW turbo engines, especially the N54 and many N55 applications, 30FF is one of the most common and most searched faults.