U1804 Volkswagen W12 Diagnostic Trouble Code

U1804 Volkswagen W12 code definition:
U1804 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Volkswagen W12.

U1804 Volkswagen W12 is defined as Cylinder 3 Injector Circuit Malfunction. This code means the PCM (powertrain control module, also known as ECM or engine control) has detected a problem in the injector or its wiring, or in injector circuit for cylinder 3. The PCM then uses this data to provide the right strategies for the fuel delivery and ignition timing of the engine.

Symptoms

Symptoms of a U1804 Volkswagen W12 diagnostic trouble code may include:
Place of U1804 in engine

Possible Causes :

  • A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
  • Faulty IMRC actuator relay (if equipped)
  • An air leak forward of the DPF will change the sensor readings resulting in the code

Common Misdiagnoses

  1. Crankshaft Position Sensor Circuit Performance Problem
  2. TP Sensor Learn Not Complete Problem
  3. Low Coolant Circuit Problem
  4. Cruise Control System - Vehicle Accel Too High Problem
  5. Kick-Down Switch Failed Short Problem

Repair Processes :

You might continue by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.

Process Tips

Diagnostic trouble code U1804 Volkswagen W12 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 U1804 Volkswagen W12.

Fortunately, U1804 Volkswagen W12 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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