Technical Description of OBD-II Trouble Code
The circuit B of the Cruise Control Multi-Function Input is experiencing a high voltage.
What does that mean?
This is a generic diagnostic trouble code (DTC) for powertrain issues and is commonly found in OBD-II vehicles. This code can apply to various vehicle brands such as Mazda, Alfa Romeo, Ford, Land Rover, Jeep, Dodge, Chrysler, Chevy, Nissan, and more. The specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
Cruise control is a feature designed for our comfort. Its main purpose is to maintain a manually set vehicle speed (adjusted through steering wheel buttons or multifunction switches on the steering column) without the need for the driver to control the gas pedal. In vehicles with automatic transmissions, cruise control may also adjust shift points based on real-time driving conditions.
In this case, the code suggests that the issue is related to the multifunction switch on the steering column. However, the exact location of the switch can vary between manufacturers, so it is important to refer to the service manual for accurate information. The cruise control button is a good starting point to narrow down the location. The code refers to a specific input circuit within the cruise control system, and the service manual can help identify the specific wire or circuit to focus on for diagnosis and testing.
When there is a fault in the cruise control multi-function “B” input circuit, the engine control module (ECM) will illuminate the instrument cluster with the P0593 code and related codes (P0589, P0590, P0591, P0592, and P0593).
The letter “B” in this context is used to distinguish a connector, wire, or circuit group. The manufacturer’s specifications are the best resource for understanding the meaning of this letter.
The code P0593 is set by the ECM when it detects a high electrical value in the “B” cruise control multi-function input circuit.
A cruise control stalk:
What is the severity of this DTC?
In most cases, a cruise control fault with this code has low severity and should not be a major cause for concern. However, electrical issues tend to worsen over time. The cost of fixing this fault is usually moderate. It is recommended to compare prices and obtain multiple quotes and diagnosing strategies to ensure the best outcome. Regular vehicle maintenance is always important.
What are some of the symptoms of the code?
Symptoms of a P0593 trouble code may include:
What are some of the common causes of the code?
Possible causes for the P0593 code include:
What are some P0593 troubleshooting steps?
Basic Step #1
Inspect the Multi-function/Cruise control switch for any contamination. Dirty or sticky plastic buttons/switches can cause malfunctions or abnormal operation. Ensure that the switch operates smoothly. Address any problems immediately. If your scan tool/OBD reader allows, observe the electronic operation of the switch through DATA STREAM mode.
TIP: Avoid spraying cleaning solutions directly onto the button. Use a lightly dampened clean rag with water, soap & water, or dash cleaner to remove debris from the switch’s crevices. An air-powered blow gun can help remove debris without causing further issues.
Basic Step #2
To access the connectors and harnesses involved in the cruise control/multi-function switch input circuit, you may need to remove some dash plastic/shrouds. Be careful when working with plastic. Comfortable room temperatures can make dash/interior plastic disassembly/assembly easier.
If you can easily access the connector, follow specific troubleshooting steps provided in your service manual. Switch testing will likely involve recording electrical values using a multimeter. This may include operating the switch while recording or performing static testing. Refer to the specific make and model’s service manual for a diagnostic flow chart.
Basic Step #3
ECM issues are usually the last resort in diagnosis due to their cost. It is recommended to leave ECM repairs to professionals.
