TSS Circuit Intermittent Malfunction
Your transmission speed sensor is sending an unstable or flickering signal to the engine computer, like a light switch that keeps turning on and off randomly. This intermittent connection prevents the ECU from reliably tracking transmission speed, affecting shifting and performance.
The ECU monitors the Turbine Speed Sensor (TSS) signal frequency to determine transmission input shaft speed. It expects a continuous, stable AC voltage signal that increases with engine RPM. An intermittent signal causes the ECU to detect dropouts or erratic pulses, triggering the fault code.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| TSS Signal Frequency | Continuous signal scaling with RPM (typically 0-10 kHz) | Signal dropouts, noise, or erratic pulses exceeding tolerance window |
| TSS Voltage Stability | Steady AC voltage 0-5V range | Intermittent loss of signal or voltage fluctuations below detection threshold |
Code P1906 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, P1906 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.