This could be due to several reasons:
* Faulty EGR Positive Control Solenoid Valve: This valve is responsible for controlling the flow of exhaust gases back into the intake manifold. It might be stuck open, stuck closed, or electrically faulty.
* Vacuum Leaks: The EGR system relies on vacuum to function correctly. Leaks in the vacuum lines can prevent the valve from operating properly.
* Wiring Problems: A short circuit, open circuit, or corroded connection in the wiring harness related to the EGR system can also trigger this code.
* EGR Valve itself (less likely with P1490): While less common with this specific code (P1490 focuses more on the *control* of the EGR), a severely clogged or malfunctioning EGR valve *could* indirectly cause this diagnostic trouble code.
To diagnose the problem accurately:
You'll need a mechanic or a decent OBD-II scanner capable of reading more than just the code. A simple code reader will only give you the P1490. A more advanced scanner can often provide live data, which will show whether the EGR valve is actuating correctly and what vacuum pressures are present. This allows for a more targeted approach to repair.
Simply replacing parts without a proper diagnosis could be expensive and ineffective. Start with checking the vacuum lines for leaks, and then move on to inspecting the EGR positive control solenoid valve for proper operation and electrical continuity. If you lack the experience and tools, getting a professional diagnosis is advisable to avoid unnecessary expense.
