U3855 Diagnostic Trouble Code

U3855 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 U3855 diagnostic trouble code may include:

Lack of power
Faulty O2 Sensor
Poor acceleration
Engine surge

Possible Causes :

Rarely - faulty Powertrain Control Module (PCM-programming required after replacement)
Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.
A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture.

Repair Processes :

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. It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem.

Process Tips

Diagnostic trouble code U3855 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 U3855.

Fortunately, U3855 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3855 Trouble Code For Specific Cars

U3855 Bmw 116 Calibration Memory Fault
U3855 Jensen A Seat Driver Recline Forward Switch Circuit Failure
U3855 Mercedes R Class Accessory Delay Relay Coil Circuit Short To Ground
U3855 Scion Xb Injector Circuit / IDM Codes Detected
U3855 Iveco Daily Seat Direction Switch Assembly Circuit Failure
U3855 Lancia Medusa Split Air #1 Circuit Malfunction
U3855 Nissan M 45 Column Tilt Feedback Potentiometer Circuit Short to Ground