Error Code P0591: What It Means & What To Do?

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Is your Car’s Check Engine Light and cruise control system light illuminating on the dashboard? Do you find sudden increase or decrease in vehicle speed? And is the car engine running rough with decreased performance? This might be the indication of problems with the cruise control system of the car which in other words can be an OBD code P0591 error.

OBD-II Code Cruise control will not operate is defined as a Cruise Control Multi-Function Input "B" Circuit Range/Performance.

Many modern vehicles come with cruise control systems (CCS), which sets and maintains vehicle speed. Some CCS can be set to maintain certain distance behind the lead vehicle, and can even autonomously brake in case the lead vehicle suddenly slows. On long commutes, CCS can improve traffic flow and fuel economy, as well as make it easier on the driver.

The CCS may or may not be integrated with the powertrain control module (PCM), usually depending on whether or not the vehicle is equipped with an electronic throttle control system (ETCS) or “fly-by-wire” throttle. The CCS monitors driver input, usually via a multifunction stalk or buttons on the steering wheel, and vehicle speed, modulating throttle position to maintain vehicle speed. Advanced systems may also monitor, via sonar or laser ranging systems, vehicles in front, to maintain following distance, and may also modulate electro-hydraulic braking. If the ECM detects a problem with the CCS multi-function switch, such as receiving two inputs at the same time or being unable to detect its neutral position, it will disable cruise control and set a diagnostic trouble code (DTC) in system memory. DTC P0591 is defined as “Cruise Control Multi-Function Input “B” Circuit Range/Performance.”

What causes this problem with the Cruise Control Multi-Function Input B Circuit Range/Performance?

• Faulty Speed Control Switch
• Speed Control Switch harness is open or shorted
• Speed Control Switch circuit poor electrical connection
• Blown Fuses
• PCM failure
• Poor wiring and connector issues

1. Speed Sensor - Check if the speed sensor are functioning properly and replace it immediately and it won’t allow the cruise control system to function properly.
2. Speed Sensor Connector - Sensor connectors can be faulty causing the data to be transmitted wrongly and the sensor not functioning properly. Buy new sensor connector now!
3. Cruise Control Switch - Damaged or faulty switches can be the main cause of the cruise control system not functioning properly. Replace faulty switches now!
4. Cruise Control Connector - Replace damaged connectors as they can be the main reason for the system not functioning properly. Buy new connector now!
5. Cruise Control Fuse - Blown fuses can be replaced and can be an easy solution to this OBD problem. Buy new fuses now!
6. Powertrain Control Module - PCM issues directly affects the engine control and transmission control module. Thus, replace faulty components now.
7. Diagnostic Tool - Find wide range of diagnostic tools to detect and correct the OBD code error.

Willing to know some common symptoms of OBD Code P0591? Your wish is our demand. Have a look at them below:

Common Symptoms

• Vehicle Speed Abnormal
• Check Engine Light Illumination
• Cruise control System not working
• Cruise control light illuminated irrespective for switch position
• Cruise control not getting set to desired speed

We have listed out some ways which would help you to correct the occurrence of OBD Code P0591. They are mentioned here as follows:

• Repair or replace any faulty wires
• Replacement of faulty connectors
• Damaged vacuum supply hoses repair or replacement
• Replace any blown fuses

There is no need to get strained if your OBD Code is still flashing up as we are here at your service. Have a look at our superior variety of Speed Control Switch, Cruise Control Switch, Speed Control Switch Harness, Electronic Control Module, Fuses and many more. Now all your problems would vanish within no time.

If you want to easily diagnose this fault code, then all you have to do is to follow the steps which are mentioned below:

• Check fuses, wiring harnesses, and switch for chafing, pinched wires, or obvious damage. Check connectors for bent or broken pins or corrosion and that they are firmly seated. Repair or replace as necessary.
• Depending on the vehicle, you may need to do resistance or continuity checks. Some switches use just two pins, each switch position applying a different resistance value to the circuit. Other switches use multiple pins, each switch closing or opening circuits. Check your EWD and repair manual to be sure which method your vehicle’s cruise control system switch is using.
• Disconnect the ECM and check the circuit accordingly. If continuity or resistance is correct, suspect a PCM fault or intermittent circuit problem. Do not condemn the PCM until you have rechecked the rest of the system.
• If continuity or resistance is incorrect, suspect a faulty switch or spiral cable. Repeat the check at the switch itself.
• If switch continuity or resistance is correct, suspect the spiral cable. You can check all circuits in the spiral cable end-to-end, but make sure the ignition is off, battery is disconnected, and all connectors are disconnected. If switch continuity or resistance is incorrect, replace the switch.

Common Mistakes When Diagnosing the P0591 Code

It is important to follow the correct diagnosis steps and replace the faulty components only. Always check for blown fuses and damaged wiring and connectors that can be easily replaced and can help in minimum cost for diagnosis.