U3804 Diagnostic Trouble Code

U3804 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code.

It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.

Symptoms

Symptoms of a U3804 diagnostic trouble code may include:

Possible spark knock (detonation / pre-ignition)
Poor fuel economy
The engine oil will exhibit dilution from the ECUs attempts to increase engine temperature. Some vehicles advance the fuel injection timing slightly after top center to afterburn a small amount of fuel to increase exhaust temperatures. Some of this fuel enters the crankcase. When the ECU determines the necessity to regenerate the DPF, the service life of the oil be shortened significantly
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected

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.
Defective ECU strategies or components will prevent proper regeneration

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. Check to make sure they are not burnt or corroded. If in doubt, get some Electrical Contact cleaner at any parts store if cleaning of the terminals is needed.

Process Tips

Diagnostic trouble code U3804 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 U3804.

Fortunately, U3804 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3804 Trouble Code For Specific Cars

U3804 Lincoln Aviator Throttle Position (TP) Sensor Circuit Intermittent Low Voltage
U3804 Mercedes C 280 ABS Inlet Valve Coil LR Circuit Failure
U3804 Nissan Axy Climate Control Air Temperature Internal Sensor Motor Circuit Short To Ground
U3804 Fiat Coupe Lamp Keypad Output Circuit Failure
U3804 Skoda Winnetou Lack Of HO2S22 Switch - Sensor Indicates Lean
U3804 Ford Explorer V Memory Off Switch Circuit Short to Battery
U3804 Kia Pro-ceed Second Gear Switch Circuit Malfunction