P0591: Cruise Control Multi-Function Input B Circuit Range/Performance

What does P0591 mean?

P0591 is a diagnostic trouble code indicating "Cruise Control Multi-Function Input B Circuit Range/Performance". The sensor or component is providing readings, but they fall outside the expected operating range. The part may be degraded, contaminated, or experiencing intermittent issues affecting cruise control performance.

Symptoms you may notice

• Check engine light (MIL) illuminated on dashboard
• Intermittent warning lights
• Erratic gauge readings

Common causes

• Worn or contaminated cruise control component
• Vacuum leak or intake air leak
• Clogged filter or restricted flow
• Intermittent electrical connection issue

What should you do?

This code sits in a driver assistance system such as parking sensors, cruise control, tyre pressure monitoring or a camera. The car drives normally, but the assistance may be off or, worse, half working. Do not rely on it until it has been diagnosed.