OBD-II Trouble Code Technical Description
The code indicates a high circuit in the cruise control servo control.
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that is commonly found in OBD-II vehicles equipped with cruise control. This code can be applicable to various vehicle makes such as Dodge, Chrysler, Ram, Jeep, Hyundai, BMW, Vauxhall, Mini, Chevrolet, and more.
The cruise control feature offers several benefits. It allows drivers to maintain a specified speed without constantly monitoring and adjusting according to traffic conditions and laws. By pressing a button or two, the vehicle’s sensors, solenoids, and modules work together to keep the vehicle moving at the desired speed until the driver or external factors deactivate or adjust it. Additionally, cruise control can help optimize fuel economy during long trips by considering factors that drivers may not always take into account.
The cruise control’s seamless and efficient operation is controlled by the engine control module (ECM). The ECM relies on various sensors, switches, modules, and the cruise control servo. The servo plays a crucial role in controlling the throttle when setting or adjusting the cruise control. It allows the ECM to easily and efficiently adjust the speed by controlling the throttle position. In many cases, these servos are mechanically controlled through vacuum lines and throttle cables. The vacuum to the servo is regulated by solenoids, which are controlled by the ECM. It is important to refer to the service manual to identify the specific circuit involved in diagnosing and resolving this fault.
The P0596 Cruise Control Servo Control Circuit High and related codes (P0525, P0594, and P0595) are triggered when the ECM detects a malfunction in the cruise control servo control circuit. Specifically, the P0596 code is set when a high voltage electrical condition is detected in the circuit.
Example of a cruise control servo:
What is the severity of this DTC?
I classify the severity of this code as medium. While most cruise control OBD2 fault codes are relatively minor, this code is more significant due to the direct connection between the cruise control servo and throttle control. Neglecting any active OBD2 fault code can lead to unawareness of new fault codes, which may result in more serious and costly problems, even if they are initially symptomless.
What are some of the symptoms of the code?
Some symptoms associated with the P0596 diagnostic code include:
What are some of the common causes of the code?
Possible causes of the P0596 cruise control code include:
What are some P0596 diagnostic and troubleshooting steps?
The first step in troubleshooting any malfunction is to consult the Technical Service Bulletins (TSB) for known issues related to the specific vehicle.
Advanced diagnostic steps may vary depending on the vehicle and require specialized equipment and knowledge for accurate performance. The following basic steps are provided, but it is recommended to refer to a vehicle-specific repair guide for detailed instructions.
Basic Step #1
Locate the cruise control servo, which is typically mounted in the engine compartment near the throttle body. Conduct a visual inspection, checking for fraying, kinks, corrosion, or any signs of malfunction in the servo cable. If the servo cable does not move smoothly when controlling the throttle, it may be interpreted as a performance issue by the ECM.
Inspect the physical condition of the servo, as it is usually vacuum-controlled. Check all the vacuum lines connected to the servo for cracks or deterioration, as these can indicate potential issues with the vacuum system. It is recommended to replace any cracked or deteriorated vacuum lines to prevent future problems.
Basic Step #2
Inspect the connector on the servo for any broken tabs or loose connections, and repair them if necessary. Pay attention to any areas where the harness runs through tight spaces or moving parts, as chafing can cause issues. Repair any broken or damaged wires.
Basic Step #3
If your OBD2 scan tool allows it, monitor the servo’s operation while it is connected to the vehicle. This may involve monitoring percentages or electrical values. Compare these values to the servo’s physical operation by observing it under the hood with the wheels off the ground. However, be cautious as this procedure may cause issues, especially with modern vehicles. Always ensure that any diagnosing or repair procedures are recommended by the vehicle’s manufacturer to avoid damaging other components.
