Metering Oil Pump Malfunction
The engine's metering oil pump isn't working properly, which lubricates the variable valve timing system. Think of it like a heart that's failing to pump blood efficiently to vital organs.
The ECM monitors oil pressure feedback from the metering oil pump circuit, which controls variable valve timing actuators. It detects voltage/current anomalies from the pump solenoid or pressure sensor indicating the pump isn't responding to commands or maintaining adequate flow.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Oil Pump Solenoid Current | 0.5-2.5 amps during activation | Below 0.3A or above 3.5A |
| Pump Control Voltage | 10-14.5V supply voltage | Below 8V or open circuit detected |
Code P1686 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, P1686 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.