P0723 Fault Code in Hyundai: Causes, Symptoms, and Fixes

P0723 indicates that the Transmission Control Module (TCM) is receiving an intermittent or erratic signal from the output speed sensor (OSS). This means the sensor signal is not stable, possibly dropping in and out.

Common Symptoms:

1. Check Engine Light (CEL)
2. Intermittent shifting problems (delayed, harsh, or skipped shifts)
3. Speedometer flickering or temporarily not working
4. Transmission going into limp mode randomly
5. Poor acceleration

Possible Causes:

1. Loose or corroded connector at the output speed sensor
2. Frayed or damaged wiring (especially near the transmission)
3. Faulty output speed sensor (internal short or degraded sensor)
4. Faulty or dirty reluctor ring (sensor target wheel)
5. Moisture or oil contamination in the sensor connector
6. Faulty TCM or ECM (rare, but possible)

Fixes You Can Try:

1. Inspect and reseat the OSS connector – clean any corrosion.
2. Check continuity of wiring between OSS and TCM.
3. Replace the output speed sensor if intermittent data is confirmed.
4. Scan live data while test driving – look for signal dropouts.
5. Inspect reluctor ring or tone wheel (if accessible).
6. In rare cases, update or replace the TCM if all else checks out.