C1378 Diagnostic Trouble Code

C1378 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 C1378 diagnostic trouble code may include:

Rich or lean exhaust
Fuel pressure too low
Engine surge
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)
Faulty IMRC actuator/sensor

Repair Processes :

It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem. 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. 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.

Process Tips

Diagnostic trouble code C1378 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 C1378.

Fortunately, C1378 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C1378 Trouble Code For Specific Cars

C1378 Peugeot 108 Dynamic Stability Control Right Rear Valve Malfunction
C1378 Hyundai Hcd
C1378 Rochet-schneider 30 Hydraulic Pressure Sensor Circuit Low Input
C1378 Great Wall Wingle Passenger Seat Rearward Switch Circuit Short to Battery
C1378 Citroen 11 Fan Relay (High) Circuit Malfunction
C1378 Raymond Mays 20 Fuel Volume Regulator Control Circuit High
C1378 Aston Martin Sports Air Suspension Vent Solenoid Output Circuit Short To Battery