U3801 Diagnostic Trouble Code

U3801 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 U3801 diagnostic trouble code may include:

Blown fuse (if applicable)
Engine surge
Reduction in engine performance, especially at low RPM levels
Rich or lean exhaust

Possible Causes :

Faulty IMRC actuator relay (if equipped)
A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
Dirty air cleaner element Damaged DPF

Repair Processes :

If the scan tool has that capability, and the scan tool can operate the IMRC valves, then the problem is either resolved and a simple code clearing is all that's left or a new PCM would be called for. 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 U3801 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 U3801.

Fortunately, U3801 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3801 Trouble Code For Specific Cars

U3801 Pontiac Sunbird Fog Lamp Switch Failure
U3801 Rolls-royce Silver Ghost IAT - B Sensor Intermittent
U3801 Lawil A System Too Lean (Bank 1)
U3801 Skoda 1100 IVC Solenoid Circuit Malfunction
U3801 Ford Taurus Mirror Passenger Vertical Feedback Potentiometer Circuit Open
U3801 Toyota Tundra Passenger Power Window Motor Circuit Short To Battery
U3801 Ford Torino Mirror Switch Assembly Circuit Short to Ground