B1991 Diagnostic Trouble Code

B1991 is a kind of OBD-II Diagnostic B-Body 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 B1991 diagnostic trouble code may include:

Lack of power
Faulty O2 Sensor
Poor acceleration
Reduction in engine performance, especially at low RPM levels

Possible Causes :

A faulty oxygen sensor. This will set a code in itself, however, a faulty oxygen sensor does not automatically condemn the sensor. The code just means that the sensor signal was not within specifications. An air leak or any of the above will cause an erroneous signal. There is a multitude of O2 codes relating to O2 performance which gives a clue to the problematic area.
Some aftermarket accessories and performance modifications
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 :

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. You might continue by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. Look at the plug wires to make sure they are not burnt or laying on the exhaust.

Process Tips

Diagnostic trouble code B1991 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 B1991.

Fortunately, B1991 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

B1991 Trouble Code For Specific Cars

B1991 Smart Fortwo Ii Lamp Anti-Theft Indicator Circuit Failure
B1991 Austin Maxi Aux A/C Blower Motor Relay Circuit Short to Battery
B1991 Daf 66 Gear Lever Y Position Circuit Intermittent
B1991 Daewoo Tacuma
B1991 Chrysler Centura Engine Position System Performance (Bank1)
B1991 Bugatti Type 55 Cylinder 12 Injector Circuit Low
B1991 Ford Transit Mirror Switch Reference Voltage Positive Common Open Circuit