EGI Functionality Test Failed
Your engine's computer detected that the EGR (Exhaust Gas Recirculation) system isn't working properly during its self-test. Think of it like a safety valve that's supposed to recirculate exhaust back into the engine, but the computer caught it not performing correctly.
The ECM monitors EGR valve operation by checking exhaust gas flow rates and valve position feedback during the EGI (EGR Functionality) test. The system validates that the valve opens and closes within expected parameters and that exhaust recirculation occurs at the correct flow rates.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| EGR Flow Rate | Within specification during test cycle | Below minimum or no detectable flow change |
| EGR Valve Position | Opens/closes smoothly per command | Stuck, sluggish, or no movement detected |
Code P1428 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, P1428 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.