P0403 - Exhaust Gas Recirculation (EGR) A Control Circuit/Open
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Exhaust Gas Recirculation (EGR) A Control Circuit/Open (P0403). The module sees no circuit at all — broken wire, backed-out pin, or a failed sensor.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Exhaust Gas Recirculation (EGR) A Control Circuit/Open – Coil Resistance | Resistance (Ω) | 3 - 30 Ω (typical) | Connector disconnected at 20°C |
| Exhaust Gas Recirculation (EGR) A Control Circuit/Open – Duty Cycle | PWM (%) | 5 - 95 % (modulates with target) | Engine running, actuator in control |
| Exhaust Gas Recirculation (EGR) A Control Circuit/Open – Supply Voltage | Voltage (V) | 11.8 - 14.4 V | Ignition ON at connector |
Connector disconnected at 20°C
Engine running, actuator in control
Ignition ON at connector
Oscilloscope Waveform Analysis
2 ms/div, 20 V/divPossible Causes
Open circuit, damaged wiring harness, or disconnected plug at Exhaust Gas Recirculation (EGR) A Control Circuit/Open
Channel A:Verify dedicated wiring pins and signal pair for circuit A against the schematic.
Chafed or pinched wiring harness along the signal path to Exhaust Gas Recirculation (EGR) A Control Circuit/Open
Internal mechanical wear or carbon deposits inside Exhaust Gas Recirculation (EGR) A Control Circuit/Open
Defective internal output driver or reference circuit in the control module for Exhaust Gas Recirculation (EGR) A Control Circuit/Open
Symptoms
4
Recommended Solution
Compare signal voltage and resistance between circuit A and companion circuit B at module connector.
Verify continuity (< 0.5 Ω) on the signal wire between the component plug and the ECM header connector.
Verify loaded supply voltage and harness terminal pins at Exhaust Gas Recirculation (EGR) A Control Circuit/Open.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Exhaust Gas Recirculation (EGR) A Control Circuit/Open.
Check supply and the low-side driver at the ECM connector. Replace the actuator or repair the circuit based on the readings.
Mechanic's Tip
Use the scan-tool output test with the scope on the control side at the same time. If duty changes but the actuator does not move, the valve is stuck — not the electrical fault you were chasing.
Common Combinations
P0401, P0403, P0405 Skoda Superb 2.0 TDI – EGR-Ventil N18 & Flödesavvikelse Technical Diagnostic Guide
SKODA • 68 analyses
P0401, P0403, P0405 VW 2.0 TDI EA288 – EGR-Ventil N18 & Flödesfel Diagnostic Guide (Variant 50)
VOLKSWAGEN • 60 analyses