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P0720: Output Speed Sensor Circuit Malfunction

What this check-engine code means in plain English, what usually causes it, and what a fix typically costs.

Severity: Monitor — affects transmission operation, address soon

What P0720 means

The powertrain control module (PCM) has detected an incorrect or erratic signal from the output speed sensor (OSS), which monitors the transmission output shaft speed. This sensor helps the PCM determine vehicle speed and control transmission shift points, torque converter lockup, and speedometer operation.

What causes P0720?

Likely
Faulty output speed sensorThe sensor itself has failed internally or its magnetic pickup has degraded, sending no signal or an erratic signal to the PCM.
Likely
Damaged wiring or connectorCorroded, broken, or shorted wiring between the sensor and PCM disrupts the signal, often due to exposure to road debris or transmission fluid leaks.
Possible
Transmission internal mechanical issueWorn gears, damaged reluctor ring, or internal transmission problems prevent the sensor from reading shaft speed correctly.
Less common
PCM failureThe powertrain control module itself has a fault in the circuit that reads the speed sensor signal.

Is P0720 safe to drive?

Drive it?
Usually yes, short-term with caution
Watch for
Harsh or erratic shifting, speedometer failure, transmission slipping
DIY-friendly?
Sensor replacement is moderate DIY; diagnosis requires a scan tool and multimeter.

You can typically drive short distances, but transmission shifting may be harsh, erratic, or stuck in one gear (limp mode). The speedometer may not work correctly. Prolonged driving with faulty shift timing can cause additional transmission wear, so have it diagnosed promptly.

P0720 repair cost

~$100 – $400+

Industry-average estimates. Cost depends on whether it's just the sensor and wiring or requires transmission disassembly to access internal components or the reluctor ring.

Which one is it for your car?

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