U3666 Diagnostic Trouble Code

U3666 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 U3666 diagnostic trouble code may include:

Malfunction Indicator Lamp (MIL) illuminated
Carbon Buildup on O2 Sensor
Poor fuel economy
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.
Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.

Repair Processes :

Find out what kind of system you have and verify that voltage to the fuel level sensor is present at the fuel pump wiring harness. 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. Pack the connector cavity with dielectric silicone compound (same stuff they use for light bulb sockets and spark plug wires) and reassemble.

Process Tips

Diagnostic trouble code U3666 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 U3666.

Fortunately, U3666 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3666 Trouble Code For Specific Cars

U3666 Honda Acura Rl Pressure Control Solenoid B Performance
U3666 Studebaker President Lamp Warning Relay Circuit Failure
U3666 Matra-simca Murena Transmission Overtemperature Condition
U3666 Chevrolet Xp Engine Coolant Temperature Circuit Malfunction
U3666 Lotec Sirius Torque Converter Clutch Circuit Malfuction
U3666 Toyota Proace Park Brake Actuator Assembly Switch Released Circuit Short to Gnd
U3666 Kia Brisa Seat Rear Up/Down Potentiometer Feedback Circuit Short To Ground