Technical Description of OBD-II Trouble Code
The circuit controlling the cruise control servo is operating at a low level.
What does that mean?
This is a generic diagnostic trouble code (DTC) that applies to OBD-II vehicles with cruise control. It can be found in various vehicle makes such as Dodge, Chrysler, Ram, Jeep, Hyundai, BMW, Vauxhall, Mini, Chevrolet, etc.
The cruise control feature offers several benefits. It allows you to maintain a constant speed on long trips without constantly adjusting for traffic and traffic laws. By pressing a button or two, a combination of sensors, solenoids, and modules ensure that the vehicle maintains the specified speed until you or external factors deactivate or adjust it. Additionally, the cruise control system helps optimize fuel economy during the trip, as we often don’t consider all factors when driving to minimize costs.
The ECM (engine control module) is responsible for the smooth and efficient operation of the cruise control. It relies on various sensors, switches, modules, and the vehicle speed sensor (VSS). One crucial component is the cruise control servo, which controls the throttle when you set or adjust the cruise control. By manipulating the throttle, the ECM can easily and efficiently adjust the speed. These servos are often mechanically controlled through vacuum lines and throttle cables. The ECM controls the vacuum to the servo using solenoids, which interpret various values before determining the throttle position and speed. This fault refers to the specific circuit involved, so consult the service manual to identify the exact circuit you need to diagnose.
The P0595 Cruise Control Servo Control Circuit Low and related codes (P0525, P0594, and P0596) are triggered when the ECM detects a malfunction in the cruise control servo control circuit. In the case of the P0595, it is set when a low 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 one is more severe because the cruise control servo is directly connected to the throttle control via a cable and is responsible for throttle position at times.
It’s important to note that neglecting any active OBD2 fault code can prevent you from being aware of new fault codes. Even if there are no noticeable symptoms, leaving OBD2 fault codes unattended can lead to more serious and costly problems.
What are some of the symptoms of the code?
Symptoms of a P0595 diagnostic code may include:
What are some of the common causes of the code?
Possible causes for this P0595 cruise control code include:
What are some P0595 diagnostic and troubleshooting steps?
The first step in troubleshooting any malfunction is to research the Technical Service Bulletins (TSB) for known issues with your specific vehicle.
Advanced diagnostic steps are highly vehicle-specific and may require specialized equipment and knowledge for accurate performance. The following are basic steps, but refer to a vehicle year/make/model/powertrain specific repair guide for detailed instructions.
Basic Step #1
Typically, cruise control servos are located in the engine compartment, often near the throttle body since they control vehicle speed through it. Once located, visually inspect the servo. Check the cable for fraying, kinks, corrosion, or any signs of malfunction. If the servo cable doesn’t move freely when controlling the throttle, the ECM may interpret it as a performance issue.
Examine the physical condition of the servo, as it is usually vacuum-controlled. Any issues with the vacuum lines connected to the servo should be addressed. Replace any cracked or deteriorated lines to ensure the health of your vacuum system, as this can prevent future problems.
Basic Step #2
On the electrical side, verify the connector on the servo. Repair any broken tabs or loose connections. Pay attention to any areas where the harness runs through tight spaces or near moving parts, as chafing can cause issues. Repair any broken or damaged wires.
Basic Step #3
If your OBD2 scan tool allows it, you can monitor the servo’s operation while it is connected to the vehicle. You may receive percentages or electrical values that can be compared to its physical operation under the hood with the wheels off the ground. However, this procedure is outdated and may cause issues, especially with modern vehicles. Always ensure that any diagnosing or repair procedures are recommended by your vehicle’s manufacturer to avoid damaging other components.
