Output Speed Sensor No Signal
Your transmission's speed sensor isn't sending a signal to the engine computer, like a speedometer that stopped working. Without this feedback, the transmission can't shift properly or control itself effectively.
The ECM monitors voltage pulses from the output speed sensor (OSS) to determine transmission shaft speed and select appropriate gears. The sensor typically generates an AC or digital signal proportional to transmission output rpm. When no signal is detected for a set duration, the ECM logs fault P0723.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Output Speed Signal Frequency | Continuous AC/digital pulses proportional to vehicle speed | Zero signal or below detectable threshold for >2 seconds |
| Signal Voltage | 0.5-5V AC or 0-5V digital | No voltage variation detected |
Code P0723 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, P0723 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.