U3491 Diagnostic Trouble Code

U3491 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 U3491 diagnostic trouble code may include:

Blown fuse (if applicable)
Engine surge
Reduction in engine performance, especially at low RPM levels
The engine oil will exhibit dilution from the ECUs attempts to increase engine temperature. Some vehicles advance the fuel injection timing slightly after top center to afterburn a small amount of fuel to increase exhaust temperatures. Some of this fuel enters the crankcase. When the ECU determines the necessity to regenerate the DPF, the service life of the oil be shortened significantly

Possible Causes :

Defective ECU strategies or components will prevent proper regeneration
The Mass Airflow sensor is a hot wire that senses the volume of air entering the intake manifold. The computer uses this information to control fuel mixture.
Dirty air cleaner element Damaged DPF

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. 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. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.

Process Tips

Diagnostic trouble code U3491 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 U3491.

Fortunately, U3491 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3491 Trouble Code For Specific Cars

U3491 Renault Eight Gear Shift Position Circuit Range/Performance
U3491 Grant Six Passenger Power Window Motor Circuit Short To Ground
U3491 Saab Gt Ignition Tamper Circuit Short To Battery
U3491 Opel Corsa Decklid Release Circuit Open
U3491 Renault Scenic High Clutch Drum Speed Sensor Malfunction
U3491 Seat Altea Injector Circuit Malfunction - Cylinder 8
U3491 Mega Monte Carlo A/C Refrigerant Temperature Sensor/Circuit Malfunction