P2521 Diagnostic Trouble Code

P2521 is a kind of OBD-II Diagnostic P-Powertrain 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 P2521 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 :

Look for rubbing, scraping, bare wires, worn spots or melted plastic connectors. Pull the connectors apart and carefully look at the terminals (the metal parts) inside the connectors. 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 P2521 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 P2521.

Fortunately, P2521 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P2521 Trouble Code For Specific Cars

P2521 Skoda 110 IPR Circuit Failure
P2521 Tchaika Tchaika Mirror Switch Reference Voltage Positive Common Supply Voltage Fault
P2521 Honda N Iii PWM Input Circuit Failure
P2521 Vector M PRNDL Reverse Input Open Circuit
P2521 Lanchester 30 Speed Control Unable to Hold Speed
P2521 Volkswagen Polo 4 Rotor Control Fault
P2521 Seat 133 Injector Circuit Malfunction - Cylinder 2