Brake Switch Out Of Self Test Range
Your brake pedal switch isn't sending the right signal during the computer's self-check, like a light switch that doesn't click properly into place. The ECU expects to see specific voltage changes when you press the brake, but it's reading something outside the acceptable range.
The ECU monitors the brake switch signal voltage during self-test to verify it transitions correctly between on and off states. The switch should show distinct voltage levels—high when brake is released and low when pressed. If the signal falls outside the expected thresholds, the ECU can't confirm proper brake function.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Brake Switch Voltage (Released) | 4.5-5.0V | Below 4.5V or above 5.0V |
| Brake Switch Voltage (Pressed) | 0.0-0.5V | Above 0.5V or unstable |
Code P1708 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, P1708 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.