C3974 Trouble Code

View C3974 obd/2 error code description and symptoms. C3974 engine photo

EGR Flow Insufficient Detected The EGR system is monitored during steady state driving conditions while the EGR is commanded on.
The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum. Vacuum supply EGR valve stuck closed EGR valve leaks vacuum EGR flow path restricted EGRVR circuit shorted to PWR VREF open to D.P.F. EGR sensor D.P.F. EGR sensor downstream hose off or plugged EGRVR circuit open to PCM VPWR open to EGRVR solenoid D.P.F. EGR sensor hoses both off D.P.F. EGR sensor hoses reversed Damaged EGR orifice tube Damaged EGRVR solenoid Damaged PCM Perform KOER self-test and look for DTC C3974 as an indication of a hard fault.

A good starting point in your diagnosis is checking all system fuses and fusible links. This can be done using the DVOM on the voltage setting. You will want to test the fuses with circuits loaded. Some fuses will appear normal until a load is placed on their respective circuit; at which point they will fail. This has been the cause of many 'phantom malfunctions'. Consult your vehicle information source for fuse and fusible link locations. If all fuses are in working order, you may want to check TCM relay operation by swapping identical relays. Usually the horn relay, starter relay, fuel pump relay, air conditioning clutch relay, and controller relays are similar enough in design to swap for diagnostic purposes.

C3974 Error Code Repair Process :

If your air suspension secondary front inflator solenoid output circuit failure check engine light is illuminated, it's best to take it in for diagnostic testing, which can feel like a hassle. Because while the lights vary in appearance from vehicle to vehicle, all have the same basic meaning: There's a problem with the car's emissions system. The on-board diagnostics system C3974 and engine control unit are in charge of monitoring a bunch of different air suspension secondary front inflator solenoid output circuit failure, and if they get a reading that's a little out of whack, up pops the check engine light.

C3974 is a kind of Chassis Trouble Code

Diagnosing chassis noises can be one of the most frustrating problems technicians face. Fortunately, manufacturers have engineered noise, vibration and harshness (NVH) diagnostic techniques and equipment to find the source of the noise.

Common Causes of C3974

A common cause of code C3974 is the failure of Air Suspension Secondary Front Inflator Solenoid Output Circuit Failure, but there are several other possible causes as well, such as ;

Air fuel ratio (A/F) Sensor 1 Bank 1 circuit poor electrical connection
Faulty Mass Air Flow (MAF) sensor
Fuel Injectors circuit poor electrical connection
Improper ignition timing

C3974 Trouble Code

C3974 Error Code Repair Process :

Common Causes of C3974

C3974 code for all cars