Output Speed Sensor Intermittent
P0723 indicates the transmission Output Speed Sensor (OSS) is sending an intermittent or no signal to the PCM. This sensor measures transmission output shaft speed, which is critical for proper shift timing and torque converter operation. When the signal is lost or unreliable, the transmission cannot shift correctly and the engine may enter limp mode.
What You Might Notice
- Check Engine Light illuminated
- Transmission does not shift or shifts roughly
- Poor fuel economy
- Speedometer shows incorrect or erratic reading
- Engine may enter limp mode with reduced power
Most Common Causes
- 1
Defective Output Speed Sensor
The OSS sensor has failed or is producing an intermittent signal. This is the most common cause and typically requires sensor replacement.
- 2
Corroded or damaged wiring/connectors
The sensor wiring harness or connector terminals have corrosion, breaks, or loose connections preventing signal transmission to the PCM.
- 3
Dirty transmission fluid or clogged filter
Contaminated fluid can cause sensor malfunction and restrict hydraulic passages needed for proper transmission operation and sensor function.
- 4
Defective Transmission Valve Body or Shift Solenoid
Internal transmission components may be faulty, affecting transmission response and creating conditions that trigger the OSS code.
How to Diagnose It
- 1
Check Defective Output Speed Sensor — The OSS sensor has failed or is producing an intermittent signal. This is the most common cause and typically requires sensor replacement.
- 2
Check Corroded or damaged wiring/connectors — The sensor wiring harness or connector terminals have corrosion, breaks, or loose connections preventing signal transmission to the PCM.
- 3
Check Dirty transmission fluid or clogged filter — Contaminated fluid can cause sensor malfunction and restrict hydraulic passages needed for proper transmission operation and sensor function.
- 4
Check Defective Transmission Valve Body or Shift Solenoid — Internal transmission components may be faulty, affecting transmission response and creating conditions that trigger the OSS code.
How to Fix It
- 1
Replace Output Speed Sensor
Locate the OSS (typically mounted on the transmission housing) and replace with a new sensor. Ensure proper connector seating and check wiring for damage before installation.
- 2
Inspect and repair wiring harness
Check the OSS wiring and connector for corrosion, breaks, or poor connections. Clean corroded terminals with electrical contact cleaner or replace damaged wiring sections.
- 3
Change transmission fluid and filter
Drain old transmission fluid and replace with manufacturer-specified fluid and new transmission filter. Contaminated fluid can impair sensor operation.
- 4
Scan for additional codes and test PCM
Use a diagnostic scanner to check for related transmission codes. If wiring and sensor are good, the transmission valve body or PCM may require professional diagnosis or replacement.
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