P0591 Fault Code

Cruise Control Multi-Function Input B Circuit Range/Performance

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0591 fault code indicates an issue with the Cruise Control Multi-Function Input B circuit, specifically related to its range or performance. This fault generally implies a malfunction in the system that controls cruise control functions, potentially affecting vehicle speed regulation. It may arise from wiring problems, sensor failures, or issues with the cruise control module itself.

What are the symptoms of the P0591 code?

Drivers may experience several symptoms when the P0591 code is triggered, such as:

• Inability to set or maintain cruise control.
• Unresponsive cruise control functionalities.
• Warning lights on the dashboard, usually including the cruise control indicator.
• Erratic vehicle speed or unexpected acceleration/deceleration.

What causes the P0591 code?

Common causes of the P0591 fault code may include:

• Damaged or corroded wiring in the cruise control input circuit.
• Faulty cruise control switch or input device.
• Defective Engine Control Module (ECM) or cruise control module.
• Poor ground connections or loose harness connections.
• Faulty throttle position sensor or other related sensors.

How to fix P0591?

To resolve a P0591 fault code, the following steps can be taken:

• Inspect wiring and connectors for damage or corrosion; repair or replace as necessary.
• Test and, if needed, replace the cruise control switch or input device.
• Check and update the ECM or cruise control module firmware if applicable.
• Ensure that ground connections are secure and free from corrosion.
• Diagnose any related sensors (like throttle position) and replace faulty components.