Intake Manifold Runner Control Circuit Malfunction
The engine's intake manifold has movable flaps that optimize airflow, but the computer detected an electrical problem with the circuit controlling them. Think of it like a dimmer switch that's broken—the light won't respond when you try to adjust it.
The ECU monitors voltage and current flow to the intake manifold runner control (IMRC) solenoid or motor. It detects open circuits, shorts, or resistance values outside expected ranges. The system expects smooth electrical transitions when commanding the runners open or closed.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Solenoid Control Voltage | 12V when activated, 0V at rest | No voltage change or stuck voltage |
| Circuit Resistance | 4–8 ohms coil resistance | Open circuit (infinite) or short (under 1 ohm) |
Code P1525 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, P1525 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.