P0720 medium Severity

P0720: Output Speed Sensor Circuit Malfunction

Transmission shifting may be erratic, speedometer may be inaccurate or non‑functional, and cruise control may be disabled; continued driving can lead to limp mode or transmission damage

Overview

P0720 indicates a malfunction in the transmission output speed sensor (OSS) circuit, often caused by a faulty sensor, wiring issue, or transmission control module fault, affecting shift logic and speedometer data

Common Symptoms

  • Check Engine Light illuminated
  • Erratic, delayed, or harsh transmission shifts
  • Speedometer not reading correctly or not working
  • Poor fuel economy
  • Cruise control failure

Most Common Causes

Faulty output shaft speed sensor (OSS) high

Sensor failure or internal short results in invalid or absent speed signal to PCM/TCM

Damaged, corroded, or loose wiring/connectors in OSS circuit high

Open circuits, shorts, or poor connections interrupt sensor signal

Transmission fluid contamination or low level affecting sensor performance medium

Dirty or low fluid can impede sensor function and may accompany other issues

Faulty transmission control module (TCM) or PCM processing low

Rare; after ruling out sensor and wiring issues

Diagnostic Steps

  1. Connect OBD‑II scanner and verify that P0720 is present and record any additional related codes
    Expected: P0720 code present possibly with related OSS or transmission codes
    Interpretation: Confirms primary fault and context for further diagnosis
  2. Visually inspect the output speed sensor and its wiring harness/connectors for damage, corrosion, or loose connections
    Expected: No physical damage or corrosion; secure connectors
    Interpretation: Physical issues in harness often root cause; repair if found
  3. Using a multimeter, measure sensor resistance and signal output relative to OEM specifications
    Expected: Resistance and output signal within spec
    Interpretation: Out‑of‑spec readings indicate sensor failure
  4. Check transmission fluid level and condition
    Expected: Fluid at proper level and clean
    Interpretation: Contaminated or low fluid may affect sensor operation
  5. If wiring and sensor test good, evaluate PCM/TCM functionality and signal integrity using live data
    Expected: Proper signal timing and values between modules
    Interpretation: Inconsistent live data may point to module fault

Repair Solutions

Replace output shaft speed sensor medium
Estimated Cost: $50 - $500

Cost varies widely by vehicle model and part quality

Repair or replace damaged wiring/connectors in sensor circuit medium
Estimated Cost: $20 - $200

Includes harness repair, connector cleaning, and secure fitting

Flush and replace contaminated or degraded transmission fluid easy
Estimated Cost: $100 - $250

Improves sensor environment; usually adjunct to primary fixes

Replace or reprogram PCM/TCM if confirmed faulty hard
Estimated Cost: $300 - $1200

Last resort after confirming sensor/harness are functional

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing output speed sensor without checking wiring harness damage
  • Assuming a PCM/TCM fault before ruling out sensor and harness issues
  • Ignoring transmission fluid condition as contributing factor

Frequently Asked Questions

Can you explain the meaning of P0720?

The P0720 code stands for Output Speed Sensor Circuit Malfunction. This generally indicates an issue with the Sensors system.

Is it safe to drive with a P0720 code?

You should treat P0720 as a medium issue. Transmission shifting may be erratic, speedometer may be inaccurate or non‑functional, and cruise control may be disabled; continued driving can lead to limp mode or transmission damage

How do I know if I have code P0720?

You may experience the following: Check Engine Light illuminated, Erratic, delayed, or harsh transmission shifts, Speedometer not reading correctly or not working.

What causes the P0720 code?

The most common causes are: Faulty output shaft speed sensor (OSS), Damaged, corroded, or loose wiring/connectors in OSS circuit, Transmission fluid contamination or low level affecting sensor performance.

What is the price difference for fixing P0720?

It depends on what needs to be fixed. Repair or replace damaged wiring/connectors in sensor circuit repairs are cheaper (~$200), while Replace or reprogram PCM/TCM if confirmed faulty repairs are on the higher end (~$1200).

Does P0720 affect Ford, Toyota, or Honda?

This is a universal code. You might see P0720 on Ford, Chevrolet, Toyota, Honda, Nissan, or any other OBD-II vehicle.

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