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P0720: Output Speed Sensor Circuit Malfunction

Severity: medium

What it means: The transmission or engine computer isn't getting a valid signal from the transmission output shaft speed sensor. That sensor helps the computer decide when to shift and what the vehicle speed is.

Safe to drive? Use caution. Harsh shifts, limp mode, a dead or erratic speedometer, and lost cruise control are common. Avoid highway trips until it is diagnosed.

Common symptoms

Likely causes, ranked

  1. Faulty transmission output speed sensorShop
  2. Damaged wiring or connector at the sensorDIY or shop
  3. Low, dirty, or wrong transmission fluidShop
  4. Valve body, TCM, or related internal issueShop
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Vehicle-specific notes

  • 2014–2019 Infiniti Q70: Owners and shops often see P0720 with P0500 when the 7-speed feels like it slips into neutral at low speed; valve body replacement is a common repair path discussed with those codes. Read the full answer · Source

Answers that mention P0720

DIY or shop?

Sensor and wiring checks can be DIY on some cars; valve body and TCM work are shop jobs.

Before you replace parts

  1. Read freeze-frame data and note related codes (P0500, P0722, gear-ratio codes).
  2. Inspect the output speed sensor connector for corrosion or a broken wire.
  3. Verify transmission fluid level and condition the OEM way.
  4. Clear the code only after a repair, then confirm it stays off on a road test.

Vehicle notes

  • Infiniti Q70 2014–2019: Owners and shops often see P0720 with P0500 when the 7-speed feels like it slips into neutral at low speed; valve body replacement is a common repair path discussed with those codes. Source: https://www.reddit.com/r/infiniti/comments/1ghx4u8/problem_with_transmission/

Safety / mechanic note

Verify with a mechanic. A bad output speed signal can put the transmission in limp mode or cause harsh shifts that surprise you in traffic. A code points to a circuit or system, not always a specific part.

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Sources