U3878 Diagnostic Trouble Code

U3878 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 U3878 diagnostic trouble code may include:

Corroded or damaged connector
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
Lack of power
Diminished fuel efficiency

Possible Causes :

Faulty IMRC actuator/sensor
A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture.
Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.

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. 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.

Process Tips

Diagnostic trouble code U3878 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 U3878.

Fortunately, U3878 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3878 Trouble Code For Specific Cars

U3878 Triumph Renown PATS Received Invalid Format Of Key-Code From Ignition Key Transponder
U3878 Mercedes-benz Bionic Air Conditioner Refrigerant Charge Loss
U3878 Ford Trend Misfire Monitor AICE Chip Fault
U3878 Toyota F-1 O2 Sensor Signals Swapped Bank 1 Sensor 1/ Bank 2 Sensor 1
U3878 Healey Silverstone Passenger's Front Seat Up Switch Circuit Short to Battery
U3878 Mercedes-benz Cl Class Air Pressure Low Circuit Short to Gnd
U3878 Toyota Avensis O2 Sensor Circuit High Voltage (Bank 1 Sensor 3)