C0781 Diagnostic Trouble Code

C0781 is a kind of OBD-II Diagnostic C-Chassis 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 C0781 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
The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.

Possible Causes :

Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.
Rarely - faulty Powertrain Control Module (PCM-programming required after replacement)
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 :

Look at the plug wires to make sure they are not burnt or laying on the exhaust. 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. Check to make sure they are not burnt or corroded. If in doubt, get some Electrical Contact cleaner at any parts store if cleaning of the terminals is needed.

Process Tips

Diagnostic trouble code C0781 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 C0781.

Fortunately, C0781 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C0781 Trouble Code For Specific Cars

C0781 Toyota Ipsum Oil Level Switch Circuit Failure
C0781 Aston Martin Rapide Air Suspension Vent Solenoid Output Circuit Open
C0781 Enzmann 506 Injection Pump Fuel Metering Control "B" Low (Cam/Rotor/Injector)
C0781 Hyundai Entourage SCP (J1850) Invalid or Missing Data for Air Conditioning Clutch
C0781 Jaguar D-type Seat Driver Forward Circuit Short To Battery
C0781 Citroen Activa Flash To Pass Switch Circuit Short To Ground
C0781 Lancia Lybra Speed Wheel Sensor RR Input Open Circuit