B0257 Mercedes-benz S Diagnostic Trouble Code

B0257 Mercedes-benz S code definition:
B0257 is a kind of OBD-II Diagnostic B-Body Diagnostic Trouble Code for Mercedes-benz S.

B0257 Mercedes-benz S is described as Fuel Rail Pressure Sensor Circuit Malfunction. This code is strictly about the incoming signal from the FRP (fuel rail pressure) sensor falling below the calibrated limit for a certain period of time. There are two wires dedicated for each coil; one is battery feed which usually comes from the distribution center, and the other one for the coil driver circuit from the PCM. The PCM grounds or ungrounds the circuit to activate or deactivate the coil.

Symptoms

Symptoms of a B0257 Mercedes-benz S diagnostic trouble code may include:
Place of B0257 in engine

Possible Causes :

  • Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.
  • Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.
  • Some aftermarket accessories and performance modifications

Common Misdiagnoses

  1. Control Module Throttle Actuator Position Performance Problem
  2. Air Conditioning (A/C) Clutch Feedback Circuit High Voltage Problem
  3. Cruise Vehicle Speed/Set Speed Difference Too High Problem
  4. Kick-Down Switch Failed Short Problem
  5. Park/Neutral Postion (PNP) Switch Circuit Engine Torque Signal Circuit Problem

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications.

Process Tips

Diagnostic trouble code B0257 Mercedes-benz S is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before B0257 Mercedes-benz S.

Fortunately, B0257 Mercedes-benz S is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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