B2521 Diagnostic Trouble Code

B2521 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 B2521 diagnostic trouble code may include:

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
Faulty or damaged wiring
Hesitation upon acceleration
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected

Possible Causes :

A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
Faulty IMRC actuator relay (if equipped)
Defective ECU strategies or components will prevent proper regeneration

Repair Processes :

If all testing has passed so far yet you still have the same code, check your scan tool and see if it can open and close the IMRC valve. 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.

Process Tips

Diagnostic trouble code B2521 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 B2521.

Fortunately, B2521 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

B2521 Trouble Code For Specific Cars

B2521 Gaz 22 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
B2521 Dacia Logan Fuel Temperature Sensor A Circuit low Input
B2521 Ferrari 801 Intake Valve Control Solenoid Circuit Range/Performance (Bank 2)
B2521 Ferrari California Interior Fan Control Circuit Short to Ground
B2521 Mercedes-benz 290 Air Bag Passenger Circuit Short To Ground
B2521 Royce 1904 Ignition Retard Request Circuit Fault
B2521 Saturn Astra Illuminated Entry Relay Short To Ground