P1956 Diagnostic Trouble Code

P1956 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 P1956 diagnostic trouble code may include:

Faulty or damaged wiring
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
Poor fuel economy
Rich or lean exhaust

Possible Causes :

Faulty IMRC actuator relay (if equipped)
A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture.

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 P1956 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 P1956.

Fortunately, P1956 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P1956 Trouble Code For Specific Cars

P1956 Plymouth Trail Duster Exhaust Gas Recirculation Circuit Range/Performance
P1956 Ac 3000 A/C Request Signal Circuit Short to Ground
P1956 Proton Saga Flx Fuel System Leak Detected Small Leak
P1956 Smart Fortwo Ii Lamp Anti-Theft Indicator Circuit Failure
P1956 Fiat 35 Hp Lamp Air Bag Warning Indicator Circuit Failure
P1956 Toyota Sa Park Switch Indicates Park with Vehicle Moving
P1956 Seat Ronda Input shaft speed signal missing/faulted