U0303 Volkswagen Polo 4 Diagnostic Trouble Code

U0303 Volkswagen Polo 4 code definition:
U0303 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Volkswagen Polo 4.

U0303 Volkswagen Polo 4 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. 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 U0303 Volkswagen Polo 4 diagnostic trouble code may include:
Place of U0303 in engine

Possible Causes :

  • An air leak forward of the DPF will change the sensor readings resulting in the code
  • Rusty exhaust systems, cracked exhaust manifolds or damaged or missing gaskets or donuts will cause air leaks.
  • Fuel with a large percentage of sulfur will clog the DPF quickly

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 :

It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem. With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground.

Process Tips

Diagnostic trouble code U0303 Volkswagen Polo 4 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 U0303 Volkswagen Polo 4.

Fortunately, U0303 Volkswagen Polo 4 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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