Technical Description of OBD-II Trouble Code
The circuit for the Cruise Control Multi-Function Input A is stuck.
What does that mean?
This is a generic diagnostic trouble code (DTC) for powertrain issues in OBD-II vehicles. It can apply to various vehicle brands such as Mazda, Alfa Romeo, Ford, Land Rover, Jeep, Dodge, Chrysler, Chevy, Nissan, etc. The repair steps may vary depending on the year, make, model, and powertrain configuration.
Cruise control is designed for our comfort. Its main purpose is to maintain a manually set vehicle speed (via steering wheel buttons, multifunction switch mounted to the steering column, etc.)
With cruise control, the operator doesn’t have to control the gas pedal, and if the vehicle has an automatic transmission (A/T), it can also adjust shift points based on real-time driving conditions.
In this case, it seems that the issue is related to the multifunction switch on the steering column. However, the location may vary between manufacturers, so further research is necessary. Start by checking the cruise control button to narrow down the possible locations. This code refers to a specific input circuit within the cruise control system. Consult the service manual to determine which wire/circuit needs to be diagnosed/tested.
When there is a fault in the cruise control multi-function “A” input circuit, the engine control module (ECM) will illuminate the instrument cluster with codes P0578 and related codes (P0564, P0578, P0579, P0580, and P0581).
The letter “A” in this context could be used to distinguish a connector, wire, circuit group, etc. Consult the manufacturer’s specifications for the best resource.
The ECM sets code P0590 when the “A” cruise control multi-function input is electronically or mechanically “stuck”.
A cruise control stalk:
What is the severity of this DTC?
This DTC has low severity for most cruise control faults, although there may be exceptions. In general, this fault should not cause serious concern. However, electrical issues tend to worsen over time. The cost of fixing this fault is usually moderate.
Keep in mind that severity can be subjective, so it’s important to compare prices and get multiple quotes and diagnosing strategies. Work orders alone may help pinpoint the issue. Always stay on top of general vehicle maintenance.
What are some of the symptoms of the code?
Symptoms of a P0578 trouble code may include:
What are some of the common causes of the code?
Causes for this P0578 code may include:
What are some P0578 troubleshooting steps?
Basic Step #1
Once you locate your vehicle’s multi-function/cruise control switch, visually inspect it for any contamination. Plastic buttons/switches can easily get dirty, greasy, or sticky, causing 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 (the mode name may vary).
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 worsening the situation.
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, you may be able to apply specific troubleshooting steps from your service manual. Switch testing will likely involve recording electrical values using a multimeter. This may include operating the switch while recording and/or static testing. Refer to the specific make and model’s service manual for a diagnostic flow chart.
Basic Step #3
A problem within the ECM is usually the last resort in diagnosis. Since it can be one of the most expensive electronic repairs for your vehicle, leave it to the professionals.
