B3785 Mercedes CL 600 Diagnostic Trouble Code

B3785 Mercedes CL 600 code definition:
B3785 is a kind of OBD-II Diagnostic B-Body Diagnostic Trouble Code for Mercedes CL 600.

B3785 Mercedes CL 600 is described as Oxygen Sensor Circuit No Activity Detected (Bank 1, Sensor 1). This means there's a problem in the front oxygen sensor on Bank 1, as the O2 sensor is inactive. Any code that causes the vehicle's engine to die while running should be fixed as soon as possible, as it can be dangerous for both the vehicle and the passengers of the vehicle.

Symptoms

Symptoms of a B3785 Mercedes CL 600 diagnostic trouble code may include:
  • Faulty PCM
  • The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
  • Poor acceleration
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
Place of B3785 in engine

Possible Causes :

  • Fuel with a large percentage of sulfur will clog the DPF quickly
  • The Mass Airflow sensor will also cause this problem. Mass Airflow circuit malfunction.
  • A large air leak at or near the number one oxygen sensor would also cause a lean mixture.

Common Misdiagnoses

  1. Exhaust Gas Recirculation System Valve 1 Problem
  2. BBV Sensor Circuit Low Voltage Problem
  3. Transmission Engaged At High Throttle Angle Problem
  4. Cruise Inhibit Control Circuit Problem
  5. TFP Valve Position Switch-Drive Without Drive Ratio Problem

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition. It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem.

Process Tips

Diagnostic trouble code B3785 Mercedes CL 600 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 B3785 Mercedes CL 600.

Fortunately, B3785 Mercedes CL 600 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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