Exhaust Gas Recirculation Control Circuit Low
The EGR control circuit is sending a signal that's too weak or low, like a dimmer switch stuck on low. The engine computer can't properly regulate exhaust gas recirculation to reduce emissions.
The ECM monitors the voltage or current signal from the EGR control solenoid circuit. It expects a specific voltage range when commanding the solenoid open or closed. A low signal indicates a wiring issue, weak solenoid, or control circuit fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| EGR Solenoid Control Voltage | 12V nominal when activated | Below 10V or open circuit detected |
| EGR Valve Position Feedback | 0.5–4.5V (proportional) | Below 0.5V or no movement signal |
Code P0490 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0490 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.