P0859: Traction Control Input Signal High

Definition

The OBD2 code P0859 indicates that the traction control input signal is reading higher than expected, which may suggest a malfunction in the traction control system or related components

Common causes

Faulty traction control switch
Damaged wiring or connectors
Faulty traction control module
Malfunctioning brake pedal position sensor
Issues with the ABS module
Corroded or loose electrical connections
Software or calibration issues in the vehicle's control modules

Common misdiagnoses

Faulty brake switch
Malfunctioning traction control module
Defective wheel speed sensors
Wiring issues or shorts in the harness
Faulty accelerator pedal position sensor
Incorrectly calibrated ABS module
Issues with the powertrain control module (PCM)

Troubleshooting steps

1. Check for Additional Codes

Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors related to the traction control system. Look for frayed wires, corrosion, or loose connections that could cause a poor signal
4. Pay special attention to the connectors at the traction control module and any associated sensors
5. Test the Traction Control Switch
6. If your vehicle has a traction control switch, test it to ensure it is functioning correctly. A faulty switch could send an incorrect signal to the traction control module
7. Check the Traction Control Module
8. Inspect the traction control module for any signs of damage or corrosion. If possible, test the module to ensure it is functioning properly
9. If you have access to a scan tool, you may be able to monitor the inputs and outputs of the module to see if it is receiving and sending the correct signals
10. Inspect the Brake System
11. Since traction control systems often rely on brake system inputs, check the brake pedal position sensor and any related components. Ensure they are functioning correctly and that there are no issues with the brake system
12. Test the Wheel Speed Sensors
13. The traction control system relies on wheel speed sensors to determine if any wheels are slipping. Test these sensors for proper operation and check their wiring for damage
14. Ensure that the sensors are clean and free from debris
15. Check for Ground Issues
16. Ensure that all ground connections related to the traction control system are secure and free from corrosion. Poor grounding can lead to erratic signals
17. Clear Codes and Test Drive
18. After performing any repairs or adjustments, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns
19. If the issue persists, consult the vehicle's service manual for specific diagnostic procedures related to the traction control system. This may provide additional insights or steps tailored to your vehicle
20. Seek Professional Help
21. If you are unable to resolve the issue after these steps, it may be best to consult a professional mechanic or technician who has experience with your vehicle's make and model. By following these troubleshooting steps, you should be able to identify and address the cause of the P0859 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check for Additional Codes

2. Inspect Wiring and Connectors

3. Visually inspect the wiring and connectors related to the traction control system. Look for frayed wires, corrosion, or loose connections that could cause a poor signal

4. Pay special attention to the connectors at the traction control module and any associated sensors

5. Test the Traction Control Switch

6. If your vehicle has a traction control switch, test it to ensure it is functioning correctly. A faulty switch could send an incorrect signal to the traction control module

7. Check the Traction Control Module

8. Inspect the traction control module for any signs of damage or corrosion. If possible, test the module to ensure it is functioning properly

9. If you have access to a scan tool, you may be able to monitor the inputs and outputs of the module to see if it is receiving and sending the correct signals

10. Inspect the Brake System

11. Since traction control systems often rely on brake system inputs, check the brake pedal position sensor and any related components. Ensure they are functioning correctly and that there are no issues with the brake system

12. Test the Wheel Speed Sensors

13. The traction control system relies on wheel speed sensors to determine if any wheels are slipping. Test these sensors for proper operation and check their wiring for damage

14. Ensure that the sensors are clean and free from debris

15. Check for Ground Issues

16. Ensure that all ground connections related to the traction control system are secure and free from corrosion. Poor grounding can lead to erratic signals

17. Clear Codes and Test Drive

18. After performing any repairs or adjustments, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

19. If the issue persists, consult the vehicle's service manual for specific diagnostic procedures related to the traction control system. This may provide additional insights or steps tailored to your vehicle

20. Seek Professional Help

21. If you are unable to resolve the issue after these steps, it may be best to consult a professional mechanic or technician who has experience with your vehicle's make and model. By following these troubleshooting steps, you should be able to identify and address the cause of the P0859 code