P0403 fault code: EGR control circuit fault
Plain-language definition
EGR A Control Circuit/Open
What does it mean?
The engine computer controls the EGR valve through an electrical circuit; depending on the engine, the valve is opened and closed by a solenoid or a small electric motor. The engine computer constantly monitors the voltage or current in this circuit.
P0403 means the engine computer has read an unexpected electrical value in this circuit, such as an open circuit (a break). This isn't a flow measurement but a circuit check: the problem may be in the wiring, the connector or the valve's internal winding. On engines with more than one EGR valve or circuit, the "A" in the code's definition tells which one is meant.
The symptoms depend on the position the valve is stuck in. If the valve can't open, there may be no difference while driving; if it's stuck open, there may be rough idling and a loss of power. On some cars the engine computer may limit power to protect the engine.
How serious is it?
This is a Warning-level code. Until the circuit fault is fixed, the engine computer can't control the EGR valve properly; this can affect emissions and, on some cars, how the engine runs.
Severity is a guide; if the warning light is flashing or you notice symptoms while driving, have the car checked at a workshop.
Common general causes
- Loose or corroded EGR valve connector
- Break, chafing or short circuit in the wiring harness
- Fault in the internal winding of the EGR valve or its solenoid
- Fuse or relay problem in the power supply (on some cars)
- Fault in the engine computer's driver circuit (rare)
The list shows general causes; a workshop finds the actual cause on your car with a check.
Definitions by make
Some manufacturers record the same code under their own wording:
- Ford
- EGR Circuit Malfunction
- Isuzu
- EGR valve short or open - Circuit A
- Volkswagen
- Exhaust Gas Recirculation (EGR) Solenoid Control Circuit
Related codes
How does it appear in the 2dakika report?
EGR A Control Circuit/Open
If the code is read as a confirmed (stored) fault, the report shows it with the "Warning" severity; in pending or past records, codes that don't request the warning light and aren't critical appear as "Info". If the engine computer stored them, the conditions when the fault was recorded (engine temperature, rpm, speed) are shown too.
Read this code with the OBD-X1, and clear it from the app after the repair.
Clearing the code doesn't fix the fault; if the problem persists, the code comes back.