P1585 Throttle Control Unit Malfunction

Definition

Common causes

• Faulty throttle position sensor
• Malfunctioning throttle body
• Wiring issues or damaged connectors
• Faulty accelerator pedal position sensor
• Software or calibration issues in the engine control module (ECM)
• Vacuum leaks
• Electrical shorts or open circuits
• Corroded or dirty connectors
• Faulty or dirty mass air flow sensor
• Issues with the vehicle's battery or charging system

Common misdiagnoses

• Throttle Position Sensor (TPS) failure
• Accelerator Pedal Position Sensor issues
• Wiring or connector problems
• Engine Control Module (ECM) failure
• Vacuum leaks
• Idle Air Control (IAC) valve malfunction
• Mass Air Flow (MAF) sensor issues
• Fuel delivery problems
• Ignition system faults
• Mechanical issues in the throttle body

Troubleshooting steps

1. 1. Check for Additional Codes

   Use an OBD-II scanner to check for any other trouble codes that may be present. Addressing related codes can help pinpoint the issue

2. 2. Inspect Throttle Body

   Visually inspect the throttle body for any signs of dirt, carbon buildup, or physical damage. Clean the throttle body if necessary, as buildup can affect its operation

3. 3. Check Electrical Connections

   Inspect the wiring and connectors related to the throttle control unit. Look for loose connections, frayed wires, or corrosion that could affect communication

4. 4. Test Throttle Position Sensor (TPS)

   The throttle position sensor is crucial for the throttle control unit's operation. Test the TPS for proper voltage and resistance according to the manufacturer's specifications

5. 5. Inspect Accelerator Pedal Position Sensor

   Ensure that the accelerator pedal position sensor is functioning correctly. This sensor provides input to the throttle control unit, and any malfunction can trigger the P1585 code

6. 6. Check for Vacuum Leaks

   Inspect the intake system for any vacuum leaks that could affect the throttle's operation. A vacuum leak can cause erratic engine behavior and trigger codes

7. 7. Examine the Throttle Control Module

   If the above steps do not resolve the issue, the throttle control module itself may be faulty. Testing or replacing the module may be necessary

8. 8. Update or Reprogram ECU

   In some cases, a software update or reprogramming of the engine control unit (ECU) may be required to resolve the issue

9. 9. Clear Codes and Test Drive

   After performing repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns