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P0594 is a diagnostic trouble code (DTC) for "Cruise Control Servo Control Circuit/Open". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $70.00. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $30.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
The P0594 code indicates that there has been a malfunction in the electrical components of the cruise control servo control circuit, as detected by the powertrain control module, or PCM.
This code means there is a problem with the cruise control circuit. If the PCM detects an issue with the cruise control, it will run a self-instituted test of the system. If there is an abnormal result for the voltage/resistance level within the cruise control servo control circuit, it will store the OBD-II generic code P0594.
The most likely cause of an abnormal voltage/resistance level in the cruise control servo control circuit is a servo control unit that has failed, particularly in older model vehicles that integrate the servo with the cruise control module.
Other causes may include:
Before the P0594 code is detected, the cruise control will usually stop working. In most cases, the Check Engine Light will activate within two to three drive cycles after the PCM has detected the issue.
After an OBD-II scanner detects the P0594 code, a technician should begin with a visual inspection of all the wiring, connectors, and other components of the cruise control system. Any damaged elements should be replaced, reconnected, or repaired as necessary. They should then clear the code and perform a test drive, checking that the cruise control works as it should, and that the Check Engine Light does not reappear.
When diagnosing the underlying cause of the P0594 code, the most common mistake is forgetting to disconnect the PCM and the cruise control module when testing circuit resistance. It is also important to clear the code and do a road test after each potential solution is attempted. If the most common repairs do not stop the Check Engine Light from reappearing, it can be a sign of an intermittent issue that requires an in-depth inspection and servicing.
If the P0594 code is being detected, a vehicle will still be drivable. The cruise control may not be usable, but this should not affect any other function of the vehicle. However, if a fuse is blown, there may be some other minor electrical issues, such as the inability to use the radio, interior lights that will not work properly, or the inability to use the turn signal. In some cases, such as the loss of a turn signal, the car would not be safe to operate.
There are many ways that a technician can address a P0594 code detection. They include:
If a vehicle displays an unresolved P0594 code, or the code is still being stored in the PCM memory, the vehicle may not be able to pass the OBD 2 emissions test.
YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.