how to fix P0720 speed sensor code on BMW 3 Series G20/G21 (2019-2024)

BMW 3 Series G20/G21 (2019-2024)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0720

3 min read

459 words

Problem Statement

The vehicle has triggered a P0720 code, indicating a malfunction related to the vehicle speed sensor in a BMW 3 Series G20/G21 (2019-2024).

Error Code

P0720

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on the electrical systems to prevent shocks or shorts.

Symptoms

•Check engine light illuminated
•Erratic speedometer readings
•Transmission shifting issues
•Poor fuel economy
•Vehicle may enter limp mode

Diagnostic Steps

1
Scan the vehicle using an OBD-II scanner to confirm the P0720 code and check for any additional codes.
2
Inspect the vehicle speed sensor wiring and connectors for damage or corrosion.
3
Test the vehicle speed sensor output using a multimeter to ensure it’s within manufacturer specifications.
4
Check the vehicle's ECU for possible software updates or faults related to speed sensor functionality.
5
Inspect the transmission fluid level and condition, as low or contaminated fluid can affect sensor performance.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•Disconnect the negative battery terminal to prevent electrical shorts.

Parts Required

•Replacement vehicle speed sensor

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Diagnostic Steps

1
Scan the vehicle using an OBD-II scanner to confirm the P0720 code and check for any additional codes.
2
Inspect the vehicle speed sensor wiring and connectors for damage or corrosion.
3
Test the vehicle speed sensor output using a multimeter to ensure it’s within manufacturer specifications.
4
Check the vehicle's ECU for possible software updates or faults related to speed sensor functionality.
5
Inspect the transmission fluid level and condition, as low or contaminated fluid can affect sensor performance.

Solution

1. Preparation

Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, wiring diagrams.
Disconnect the negative battery terminal to prevent electrical shorts.

2. Remove the Vehicle Speed Sensor

Locate the vehicle speed sensor on the transmission (consult the service manual for exact location).
Using a socket set, remove the mounting bolts securing the speed sensor.
Carefully disconnect the wiring harness from the speed sensor.

3. Inspect and Clean

Examine the sensor for physical damage or wear.
Clean the sensor mount area and ensure no debris or metal shavings are present.
If the sensor shows signs of damage, proceed to replace it.

4. Install the New Vehicle Speed Sensor

Position the new vehicle speed sensor into the mount.
Secure it in place using the original mounting bolts. Torque them to the manufacturer’s specifications (typically around 10 Nm, but verify with the service manual).
Reconnect the wiring harness securely to the new sensor.

5. Reconnect Battery and Test

Reconnect the negative battery terminal.
Start the vehicle and perform a test drive to ensure proper operation of the speedometer and transmission shifts.