U3686 Diagnostic Trouble Code

U3686 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 U3686 diagnostic trouble code may include:

Poor fuel economy
Possible spark knock (detonation / pre-ignition)
Misfire
Rich or lean exhaust

Possible Causes :

The Mass Airflow sensor will also cause this problem. Mass Airflow circuit malfunction.
Fuel with a large percentage of sulfur will clog the DPF quickly
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 :

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. Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications.

Process Tips

Diagnostic trouble code U3686 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 U3686.

Fortunately, U3686 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3686 Trouble Code For Specific Cars

U3686 Lada Vesta Shift Solenoid C Malfunction
U3686 Toyota Solara Parking Brake Switch Circuit Failure
U3686 Chenard Walcker 3-litre Door Unlock Disarm Output Circuit Short To Ground
U3686 Reliant Scimitar Gate Select Position Circuit [senses left / right position]
U3686 Mazda Sport A/C Cycling Period Too Short
U3686 Mazda Rustler 4X4 Switch Out of Self Test Range
U3686 Simca Aronde Interior Fan Control Circuit Open