Why Speedometer on 93 Lexus LS 400 does not come until about 15 to 20 miles especially in the morning?

Potential causes and solutions:

1.Faulty Speed Sensor:

- The vehicle speed sensor is responsible for sending speed signals to the speedometer. A faulty sensor can cause inaccurate speed readings or a delayed speedometer response. Check or replace the speed sensor as needed.

2.Gauge Cluster Issues:

- In some cases, the instrument cluster itself can be the problem. Electrical faults, loose connections, or faulty components within the gauge cluster can affect speedometer functionality. Diagnose and repair any problems within the gauge cluster.

3.Transmission Issues:

- A malfunctioning transmission can affect the vehicle speed signal and, consequently, the speedometer. Check transmission fluid levels, condition, and any related sensors or components that might impact speed readings.

4.Wiring Problems:

- Damaged or loose wiring between the speed sensor, gauge cluster, and the vehicle's electronic control unit (ECU) can disrupt the signal flow. Inspect and repair any damaged wiring.

5.Diagnostic Trouble Codes (DTCs):

- Connect a diagnostic tool to your vehicle to check for any stored DTCs related to the speedometer or related systems. These codes can provide additional insight into the cause of the issue.

6.Vehicle Battery:

- A weak or malfunctioning battery can affect various electrical components, including the speedometer. Ensure the battery is in good condition and provides adequate voltage to the vehicle's electrical system.

7.ECU Issues:

- The ECU is responsible for processing various sensor inputs, including speed signals. Faults within the ECU can cause inaccurate speedometer readings. Consult a professional mechanic or a dealership for ECU diagnosis and repair if necessary.

8.Faulty Vehicle Grounding:

- Poor grounding can affect electrical components and communication between sensors and the ECU. Check and clean any ground points that may be related to the speedometer system.

9.Aftermarket Modifications:

- If your Lexus LS 400 has undergone aftermarket modifications, some alterations might interfere with the speedometer functionality. Check if any modifications were made to the electrical system, gauge cluster, or related components.

10.Professional Diagnostics:

- If you're unable to identify and fix the issue, consider taking your vehicle to a qualified mechanic familiar with Lexus vehicles. They can perform a thorough diagnosis using specialized equipment and expertise.

Remember that diagnosing automotive problems can be complex, and it's essential to approach them systematically. Start by checking the simpler causes and work your way towards more complex issues. If the problem persists or if you're unsure about any steps, seeking professional help is recommended to ensure accurate repairs.