U3686 Lada Vesta Diagnostic Trouble Code

U3686 Lada Vesta code definition:
U3686 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Lada Vesta.

U3686 Lada Vesta is defined as Ignition Coil B Primary/Secondary Circuit Malfunction.This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II tool, or vehicles made since 1996 up to present. There are two wires dedicated for each coil; one is battery feed which usually comes from the distribution center, and the other one for the coil driver circuit from the PCM. The PCM grounds or ungrounds the circuit to activate or deactivate the coil.

Symptoms

Symptoms of a U3686 Lada Vesta 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.

Common Misdiagnoses

Control Module Throttle Actuator Position Performance Problem
Air Conditioning (A/C) Clutch Feedback Circuit High Voltage Problem
Cruise Vehicle Speed/Set Speed Difference Too High Problem
Kick-Down Switch Failed Short Problem
Park/Neutral Postion (PNP) Switch Circuit Engine Torque Signal Circuit Problem

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 Lada Vesta 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 Lada Vesta.

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