Vehicle Speed Sensor Intermittent
Your vehicle's speed sensor is sending inconsistent signals to the engine computer, like a flickering speedometer that can't decide what speed you're going. This causes the ECU to lose track of your actual vehicle speed intermittently.
The ECU monitors voltage signals from the Vehicle Speed Sensor (VSS) to determine vehicle speed and control transmission shifting and fuel delivery. The sensor should produce a consistent frequency signal proportional to wheel rotation. Intermittent faults occur when the signal drops out momentarily, then returns.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| VSS Signal Frequency | Continuous pulses proportional to vehicle speed | Signal dropout lasting >500ms or erratic frequency variations |
| VSS Voltage | 0.5-4.5V alternating signal | Voltage spikes, noise, or signal loss |
Code P1505 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, P1505 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.