How is fault code P0720 fixed?

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Plug in a scanner and read every stored code plus the freeze frame data from when P0720 logged. A P0715 or input speed sensor code alongside it points you somewhere different to P0720 on its own 2. Get the car up and have a proper look at the sensor, its connector, and the loom running to it. Most of these turn out to be a damaged connector or a chafed wire rather than a dead sensor 3. Check the gearbox fluid level and condition. Burnt smell, dark colour, or glitter in the fluid tells its own story and may need sorting first 4. Back-probe the connector and check you've got a clean supply voltage and a solid earth at the sensor 5. Test the sensor itself. A scope is ideal to watch the signal while the wheels turn, but a multimeter checking resistance against the workshop spec will catch an open or shorted unit 6. Clear the code and road test. Note whether it comes straight back or only shows up intermittently, which usually means a wiring or connector fault rather than the sensor

Output Speed Sensor Circuit Malfunction

Jump to the fix

Severity

High

Can I keep driving?

Avoid extended driving; visit a service soon.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Plug in a scanner and read every stored code plus the freeze frame data from when P0720 logged. A P0715 or input speed sensor code alongside it points you somewhere different to P0720 on its own 2. Get the car up and have a proper look at the sensor, its connector, and the loom running to it.

PPowertrain
0Generic code
7Transmission
20Sequence number

What does it mean?

The TCM (transmission control module) or PCM (powertrain control module) has received an input signal from the transmission OSS (output speed sensor) or VSS (Vehicle speed sensor) that is erratic. Without a accurate output speed signal the transmission cannot properly shift the transmission or transaxle, so this code sets.

Output speed sensors detect speed by using the revolution of the output gear which is also the parking pawl gear, which is used as a reluctor (valley) for either PM generator or a Hall-Effect sensor that creates a sine or square wave pulse signal. The pulse signal is sent to the control module (TCM or PCM) which processes it as the vehicle speed.

NOTE: Whenever diagnosing a 700 series DTC (Diagnostic Trouble Code) with a transmission, transfer case or other driveline components, check for a DTC under chassis and body systems, not just under “P” or powertrain/engine or emission control type codes. Module communications DTCs are “U” codes. These are most often found when looking for DTCs under chassis or body systems.

Chassis related codes are labeled “C” and body system related codes are labeled “B” codes and these can cause drivetrain issues if they affect a sensor that is also used by the heating and air conditioning system.

Symptoms

Likely causes

How to fix it

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This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.