Hydraulic Pump Relay Circuit Range/Performance
Your car's hydraulic pump relay isn't working properly, like a switch that can't turn the pump on reliably. The engine computer detected the relay circuit isn't responding as expected.
The ECM monitors voltage and current signals from the hydraulic pump relay circuit to ensure the relay activates and deactivates at proper times. It checks for correct voltage rise, fall rates, and circuit continuity during transmission operation.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Relay coil voltage | 12V when energized, 0V when de-energized | Voltage outside expected range or fails to reach threshold |
| Circuit continuity | Less than 5 ohms resistance when relay closes | Greater than 10 ohms or open circuit detected |
Code P0946 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, P0946 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.