Vehicle Speed Sensor Out Of Self Test Range
Your vehicle's speed sensor is reading values outside the expected range during self-test, like a speedometer that's wildly off. The ECU can't verify the sensor is working correctly, so it flags this code.
The ECM monitors the Vehicle Speed Sensor (VSS) signal during self-test to ensure it falls within expected voltage or frequency ranges. If the signal is too high, too low, or absent, the ECU detects an out-of-range condition and sets the fault code. The sensor typically uses Hall effect or magnetic pickup technology to generate pulses proportional to wheel speed.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| VSS Signal Voltage | 0.5-4.5 volts (varying with speed) | Outside 0.1-5.0V or no signal detected |
| VSS Frequency | Proportional to vehicle speed (e.g., 4,000 Hz at 60 mph) | Below 10 Hz or erratic pulses during self-test |
Code P1506 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, P1506 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.