Output Speed Sensor Circuit Intermittent
The Powertrain Control Module (PCM) or Transmission Control Module (TCM) detected an erratic, dropping, or intermittent signal from the transmission output speed sensor (OSS). The computer relies on this consistent signal to determine vehicle speed, shift timing, and torque converter clutch operation.
This issue should be addressed soon because erratic shifting can cause premature transmission wear. The vehicle may also enter a protective 'limp mode' that limits speed and performance.
Common symptoms
- Illuminated Check Engine Light
- Erratic, fluctuating, or inoperative speedometer
- Harsh, delayed, or unpredictable transmission shifting
- Vehicle entering 'limp mode' (stuck in a single gear)
- Cruise control system becomes inoperative
Likely causes
- Damaged, loose, or corroded wiring and connectors at the output speed sensor
- Faulty transmission output speed sensor (OSS)
- Metal debris accumulated on the magnetic tip of the speed sensor
- Damaged or worn reluctor ring on the transmission output shaft
- Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM) (rare)
What to check before replacing parts
Visually inspect the output speed sensor wiring harness and connector.
Look for: Look for frayed wires, melted insulation, loose pins, or corrosion that could cause an intermittent electrical connection.
Remove the output speed sensor and inspect its tip.
Look for: Look for excessive metal shavings or debris on the magnetic tip, which can distort or block the magnetic signal from the reluctor ring.
Test the output speed sensor's internal resistance using a digital multimeter.
Look for: Compare the resistance reading to the manufacturer's specifications; an open circuit or out-of-range reading indicates a failed sensor.
Monitor the output speed sensor signal using an oscilloscope or an advanced scan tool while driving.
Look for: Look for sudden dropouts, spikes, or an erratic waveform/data stream that confirms the signal is intermittent.
Inspect the reluctor ring inside the transmission through the sensor mounting hole.
Look for: Look for missing, damaged, or heavily worn teeth on the ring that would cause an irregular magnetic pulse.
This page explains the generic P0723 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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