U0321 Diagnostic Trouble Code

U0321 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 U0321 diagnostic trouble code may include:

Rich or lean exhaust
Fuel pressure too low
Engine surge
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected

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)
Faulty IMRC actuator/sensor

Repair Processes :

Look for rubbing, scraping, bare wires, worn spots or melted plastic connectors. Pull the connectors apart and carefully look at the terminals (the metal parts) inside the connectors. 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. 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.

Process Tips

Diagnostic trouble code U0321 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 U0321.

Fortunately, U0321 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U0321 Trouble Code For Specific Cars

U0321 Nissan Pixo Cooling Fan Power/Ground Circuit Malfunction
U0321 Kia Sorento Iii Secondary Air Relief Solenoid Circuit Malfunction
U0321 Glas Isar Panel Dim Switch Circuit Open
U0321 Saab 9000 Ignition Run/Start Circuit Short To Battery
U0321 Ferrari Tipo Keyless Entry Circuit Short To Ground
U0321 Mg Magna Air Suspension RR Height Sensor Circuit Short To Ground
U0321 Daihatsu Materia Gear Shift Reverse Actuator Circuit Range/Performance