P0720 – Output Shaft Speed Sensor Circuit

Last updated: April 10, 2026

DTC P0720 is an ISO/SAE controlled Powertrain code that indicates an electrical circuit problem in the Output Shaft Speed Sensor Circuit. Because this is a circuit-type fault, the most productive diagnostic path is electrical: confirm the code, check for related codes, then inspect wiring and connectors before condemning any component. The control module expects a dependable electrical signal from this circuit; when voltage supply, ground integrity, signal continuity, or connector terminal condition is compromised, the module can set P0720. Intermittent opens, shorts to ground, corrosion, and poor terminal tension are common patterns that only show up under load or vibration, so voltage-drop testing and careful terminal inspection matter more than simple continuity checks.

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P0720 Quick Answer

P0720 means the control module detected a fault in the Output Shaft Speed Sensor Circuit. Because the fault type is “Circuit,” start with electrical basics: verify power and ground integrity under load, check for shorts to ground, then check for opens/high resistance from the sensor connector to the module using a wiring diagram. Closely inspect connector terminal tension and corrosion before replacing parts.

What Does P0720 Mean?

P0720 – Output Shaft Speed Sensor Circuit means the control module has detected a fault in the Output Shaft Speed Sensor Circuit. The official meaning is the same: Output Shaft Speed Sensor Circuit. This points to an electrical problem affecting the circuit the module uses to interpret output shaft speed information.

This code does not, by itself, prove a failed sensor or any internal transmission problem; it indicates the circuit is not behaving as expected. Circuit faults include missing power or ground, excessive voltage drop, an open/high-resistance path, a short to ground, or connector issues that interrupt the signal. The correct response is to test the circuit methodically and only evaluate the component after wiring, terminals, and power/ground integrity have been verified.

Theory of Operation

The Output Shaft Speed Sensor Circuit provides the control module with an electrical signal that corresponds to output shaft speed. The module monitors this circuit so it can maintain reliable speed information for control strategies that depend on output speed input. For the module, the key requirement is that the circuit produces a stable, plausible signal and that the circuit’s electrical characteristics remain within expected limits.

P0720 sets when the module detects an abnormal condition in that circuit, such as a signal that drops out, a signal pulled low by a short to ground, or a signal that cannot be interpreted because of power/ground problems or excessive resistance. Many circuit faults are intermittent and may only occur when the harness moves, temperature changes, or current demand increases. That is why loaded voltage-drop testing, short-to-ground checks, and connector terminal inspection are emphasized before replacing any parts.

Symptoms

• The malfunction indicator lamp (MIL) may illuminate because the control module detected a circuit fault.
• The speed indication may become erratic or stop working if the control module cannot reliably interpret the circuit signal.
• Transmission shifting may become harsh or inconsistent when the module cannot depend on output speed information from the circuit.
• The vehicle may enter a reduced-performance or default operating strategy if the circuit fault is persistent.
• Driveability may change intermittently if the circuit has an intermittent open or short that comes and goes with vibration or heat.
• Acceleration and deceleration behavior may feel abnormal when the module substitutes calculated values due to the circuit fault.
• The problem may appear only after warm-up if resistance increases in a corroded connection within the circuit.

Common Causes

• Corroded or contaminated connector terminals can add resistance, causing voltage drop and an unstable signal that the module interprets as a circuit fault.
• Loose terminal tension at the sensor or module connector can create intermittent contact, making the circuit open briefly under vibration and triggering P0720.
• A short to ground on the signal circuit can pull the signal low, preventing the module from seeing expected transitions and resulting in a circuit DTC.
• An open circuit in the signal path can prevent the module from receiving any usable signal, which the module identifies as a circuit malfunction.
• High resistance in the power feed or ground path can starve the circuit, causing the signal to distort or drop out under load and setting a circuit code.
• Harness damage (chafing, pinched wiring, or heat damage) can create intermittent opens or intermittent shorts to ground that match circuit-fault behavior.
• Poor power or ground integrity at the control module can affect its ability to interpret the incoming circuit signal, mimicking a sensor-circuit failure.

Diagnosis Steps

Tools needed: scan tool, DVOM, back-probing leads, wiring diagram.

1. Confirm the code with a scan tool and record freeze frame data. Verify whether P0720 is stored as confirmed and note any conditions shown when it set. Do not clear codes yet, because the stored data can help you reproduce the fault.
2. Check for related codes and address them in a logical order. Pay attention to other powertrain electrical or voltage-related codes because they can point to a shared power/ground issue. If multiple circuit codes appear together, prioritize system power and grounds before individual circuits.
3. Perform a thorough visual inspection of the Output Shaft Speed Sensor Circuit wiring and connectors. Look for rubbed-through insulation, pinched sections, heat damage, or signs of fluid intrusion at connectors. Gently tug-test suspected wires and observe whether insulation is brittle or cracked.
4. Verify circuit power and ground integrity under load, not just with a quick key-on voltage check. Back-probe the circuit power and ground at the connector and perform voltage-drop testing while the circuit is loaded. If you find excessive voltage drop, locate the high-resistance connection by testing segment-by-segment from the source to the load and from the load to ground.
5. Check for shorts to ground on the signal and power circuits using the wiring diagram to identify each relevant conductor. With the key off and connectors disconnected as appropriate, measure resistance to ground and look for an unintended low-resistance path. If a short is found, isolate it by separating harness sections and inspecting known rub points.
6. Check for opens or high resistance in the circuit between the sensor connector and the control module connector. Use end-to-end resistance checks and compare results to what a good conductor should show (very low resistance), then flex the harness while observing the meter for intermittent changes. If the resistance changes with movement, suspect a broken conductor inside the insulation or a loose terminal crimp.
7. Inspect connector terminals closely at both ends of the circuit. Look for spread terminals, bent pins, corrosion, discoloration, or evidence of overheating that would cause poor contact. Verify terminal tension by confirming the terminal grips the mating pin properly and repair or replace terminals that do not hold securely.
8. Recheck power and ground integrity after any connector or terminal repairs. Repeat voltage-drop testing under load to confirm the repair actually restored low-resistance current paths. If the voltage-drop values are now acceptable, proceed to verify whether the code returns.
9. Evaluate the component last, only after the circuit tests good. If the circuit has verified power, verified ground, no shorts to ground, no opens/high resistance, and good terminal tension, then suspect the sensor itself or an input interpretation issue at the module. Replace or test the component per service information only after the electrical checks support that conclusion.

Professional tip: If P0720 is intermittent, use back-probing leads and perform voltage-drop checks while gently manipulating the harness and connectors. A circuit can pass continuity checks when disconnected yet fail under load due to corrosion or weak terminal tension. Always confirm repairs by repeating the same loaded tests that exposed the fault.

Possible Fixes

• Repair or replace damaged wiring in the Output Shaft Speed Sensor Circuit where an open, high resistance, or short to ground is proven.
• Clean corrosion and restore proper terminal tension, or replace terminals/connectors that cannot maintain reliable contact.
• Repair power feed issues that cause excessive voltage drop under load, such as poor splices or degraded connections.
• Repair ground path issues proven by voltage-drop testing, including loose grounds or corroded ground connections.
• Replace the output shaft speed sensor only after confirming the circuit is electrically sound and the component is the remaining suspect.
• Repair control module power/ground supply issues if testing shows the module cannot reliably process the circuit due to poor electrical integrity.

Can I Still Drive With P0720?

Driving with P0720 can be unpredictable because a circuit fault can be intermittent and may worsen without warning as vibration, moisture, or temperature changes affect the connection. If the circuit drops out while driving, you may experience abrupt drivability changes related to how the module responds to missing or unreliable output speed information. If you notice abnormal shifting behavior, an erratic or inoperative speed indication, or any sudden change in how the vehicle responds, reduce driving and prioritize diagnosis. Avoid situations where unexpected drivability changes would create risk, and address the circuit fault promptly to prevent further complications.

How Serious Is This Code?

P0720 should be treated as moderately to potentially serious because it indicates an electrical circuit problem that can become intermittent or progress to a hard failure. Circuit faults can be caused by corrosion, damaged wiring, or poor connections that tend to worsen over time, especially if moisture intrusion is involved. While some vehicles may appear to drive normally at times, the underlying circuit integrity issue can create sudden symptoms depending on when the electrical contact is lost. The seriousness increases if the code is accompanied by unstable behavior, since that suggests the circuit fault is actively affecting operation.

Common Misdiagnoses

The most common misdiagnosis for P0720 is replacing the output shaft speed sensor immediately without proving the circuit fault with electrical testing. Another frequent error is relying on simple continuity checks with the connector unplugged and concluding the wiring is good, even though the circuit fails under load due to corrosion or weak terminal tension. Misidentifying the issue as a non-circuit problem and skipping voltage-drop testing can lead to repeated comebacks. Correct diagnosis requires confirming power/ground integrity and finding shorts to ground or opens/high resistance before replacing components.

Most Likely Fix

The most likely fix for P0720 is restoring electrical integrity in the Output Shaft Speed Sensor Circuit by repairing wiring damage or correcting connector/terminal issues that cause opens, high resistance, or shorts to ground. In many cases, cleaning corrosion, repairing a chafed section, or restoring terminal tension resolves the fault because the module can once again read a stable circuit signal. Replace the sensor only after the circuit has been verified with loaded tests and the wiring/terminals are confirmed to be sound.

Repair Costs

Repair cost depends on whether the confirmed root cause is a sensor, wiring, connector issue, or control module problem. Verify the fault electrically before replacing parts.