how to diagnose P0720 code in my BMW 3 Series F30/F31 (2012-2019)

BMW 3 Series F30/F31 (2012-2019)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0720

3 min read

507 words

Problem Statement

The P0720 code indicates a malfunction in the vehicle speed sensor circuit in the BMW 3 Series F30/F31 models from 2012 to 2019. This can lead to issues with speedometer readings

Error Code

P0720

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect battery before working on electrical systems.
•Allow the engine to cool before touching any components.

Symptoms

•Check engine light illuminated
•Erratic or non-functional speedometer
•Harsh or delayed shifting of the transmission
•ABS warning light activated
•Reduced fuel efficiency

Diagnostic Steps

1
Scan the vehicle's OBD-II system for error codes and confirm the presence of P0720.
2
Inspect the vehicle speed sensor (VSS) wiring for any visible damage, corrosion, or loose connections.
3
Measure the resistance of the VSS using a multimeter; it should be within the manufacturer's specified range.
4
Test the voltage output of the VSS while the vehicle is in motion using a multimeter.
5
Check the vehicle's transmission control module (TCM) for any stored codes or issues that could affect the VSS.
6
Inspect the vehicle’s ABS system for any faults that may be influencing the speed sensor readings.

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

•OBD-II scanner
•Multimeter
•Socket set
•Torque wrench (if required for sensor installation)

Parts Required

•Replacement vehicle speed sensor

Related Faults

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Diagnostic Steps

1
Scan the vehicle's OBD-II system for error codes and confirm the presence of P0720.
2
Inspect the vehicle speed sensor (VSS) wiring for any visible damage, corrosion, or loose connections.
3
Measure the resistance of the VSS using a multimeter; it should be within the manufacturer's specified range.
4
Test the voltage output of the VSS while the vehicle is in motion using a multimeter.
5
Check the vehicle's transmission control module (TCM) for any stored codes or issues that could affect the VSS.
6
Inspect the vehicle’s ABS system for any faults that may be influencing the speed sensor readings.

Solution

1. Preparation

Gather tools such as an OBD-II scanner, multimeter, and socket set.
Disconnect the negative battery terminal to ensure safety while working on the electrical system.

2. Inspect and Repair Wiring

Check the wiring harness connected to the VSS.
- Sub-steps:
  - Visually inspect for any frays or damage.
  - Repair or replace any damaged wires or connectors.
Reconnect the wiring harness once repairs are made.

3. Replace Vehicle Speed Sensor

If the VSS is faulty, remove it for replacement.
- Sub-steps:
  - Locate the VSS on the transmission.
  - Unplug the sensor's electrical connector.
  - Remove the mounting bolt holding the sensor in place using a socket set.
  - Pull out the old sensor and insert the new sensor in its place.
  - Secure the new sensor with the mounting bolt and reconnect the electrical connector.

4. Clear Codes and Test Drive

Reconnect the negative battery terminal.
Use the OBD-II scanner to clear the P0720 code from the system.
Perform a test drive to ensure the issue is resolved and the speedometer functions correctly.