B1521 Diagnostic Trouble Code

B1521 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 B1521 diagnostic trouble code may include:

If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
Corroded or damaged connector
Reduction in engine performance, especially at low RPM levels
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.
Fuel with a large percentage of sulfur will clog the DPF quickly

Repair Processes :

You might continue by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition. 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 B1521 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 B1521.

Fortunately, B1521 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

B1521 Trouble Code For Specific Cars

B1521 Skoda L Knock Sensor 1 Circuit Input Intermittent (Bank 1 or Single Sensor)
B1521 Mercedes-benz Gl Class Air Suspension Disable Switch Circuit Short To Ground
B1521 Monteverdi 375 Battery Power Relay Circuit Failure
B1521 Mitsubishi Gaus Autolamp Delay Increase Circuit Short To Ground
B1521 Zotye Z10hy7d Seat Belt Switch Circuit Short To Battery
B1521 Bugatti Type 64 Cylinder 2 Contribution/Balance Fault
B1521 Bmw X5 Column Reach Feedback Potentiometer Circuit Short to Battery