ECM/PCM Power Relay Sense Circuit High
The ECM/PCM power relay isn't receiving the correct voltage signal it expects, like a light switch reporting it's on when it should be off. This voltage sensing circuit is stuck at a higher level than normal, preventing proper power management.
The ECM monitors the power relay sense circuit voltage to verify the relay is switching properly and supplying stable power. It expects a voltage drop when the relay de-energizes and a rise when it energizes. A continuously high voltage indicates the relay sense line is stuck or the relay feedback circuit is open.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Relay Sense Voltage | 0.5V to 3.5V (cycling with relay state) | Above 4.5V continuously or no voltage drop detected |
| Relay Response Time | 50-200 milliseconds | No state change or excessive delay |
Code P0690 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, P0690 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.