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Error Code P0584 is defined as Cruise Control Vacuum Control Circuit Low. This means an error in the cruise control vacuum control circuit has been detected, which is usually caused by a defective cruise control switch, or damaged vacuum supply hose.
This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, particularly vehicles made from1996 up to the present day. It is particularly common but not limited to Chrysler, Chevrolet, Dodge, Ford, Hyundai, Ram, etc. Specifications on the definition, troubleshooting, and repairs vary from one powertrain model type and make and model to another.
There are many ways the vehicle goes about in controlling the cruise control system. One of the things manufacturers use is through vacuum control and the operating system.
They use the vacuum as an efficient way of controlling a cruise control servo, or similar diaphragm-type control. The vacuum control circuit plays an important role in the proper operation of the system. The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) monitors and adjusts the vacuum control side accordingly, depending on the demands of the operator’s cruise control.
If the PCM loses its monitoring capabilities to the cruise control vacuum control circuit, it will cause the cruise control system to malfunction. Many times, this system includes a vacuum solenoid, which oversees the vacuum flow to the control side of the system (i.e., controls the speed of the vehicle when the cruise is active). With this, in other systems, the responsibilities of the vacuum are consolidated to solely to the cruise control servo. As with most faults, this code could be an electrical problem caused by a mechanical issue, vice versa, or both.
While monitoring cruise control circuits, sensors, switches, etc., not to mention other systems in the vehicle, the PCM has detected the fault within the cruise control vacuum control circuit. In this case, one or more electrical values being monitored has gone out of range (i.e., beyond specifications set by the manufacturer).
Error Code P0584 appears when the PCM determines an electrical malfunction in the cruise control vacuum control circuit, specifically high voltage situation.
As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms include:
- Inoperative cruise control
- Other functions of cruise control not functioning (accel., set, resume, etc.)
- One or more cruise control functions not working properly
- Erratic vehicle speed, even when cruise control is set to a specific speed
- Cruise control light permanently in the instrument cluster
- Whistling noises coming from the engine bay
Multiple factors contribute to this code, such as:
- Damaged vacuum supply hose leading to cruise control servo
- Damaged one-way in-line check valve leading to cruise control servo
- Wiring problems (corrosion, open, short, chafed, etc.)
- Defective cruise control switch
- PCM issue (rare)
How to Check
The best start for diagnosis of this code is to check the TSB (Technical Service Bulletin) for known issues with the specific vehicle. Some vehicles may require advanced diagnostic steps and special tools, which differs from one type of vehicle to another. Here are some basic steps for diagnosis.
The first thing that must be done is to use an OBD scanner to record the freeze frame data. Mechanics also check for other additional trouble codes stored. Then, the codes must be reset, and the vehicle must be restarted to see if the code comes back.
If the code does NOT come back, that means the problem is erroneously detected, or it’s an intermittent condition.
If the code DOES come back, then electrical components must be thoroughly checked. Any damages such as blown fuses, corroded or loose connectors, damaged circuits, and shorted wires must be replaced.
Next, the vacuum supply hose must be checked. If visual inspection shows no guaranteed results, then vacuum pressure test must be done. This is where the vehicle’s service manual information comes into the picture, as mechanics have to compare the results to the specifications provided by the manufacturer.
The only way valves can be tested is by blowing through it in both directions. If it can be blown into both directions, that means it IS defective and must be replaced.
If the problem persists, then the problem could be caused by a defective cruise control switch.
How to Fix
Depending on the diagnosis, common repairs for the code include:
- Replacement of vacuum supply hose
- Replacement of one-way valve
- Replacement of damaged connectors, circuits, fuses, and wires
- Replacement of cruise control switch
The most common mistake in dealing with this code is replacing the cruise control vacuum solenoid when the problem is actually in the one-way check valve. A blown fuse is a common hidden cause as well, though it generally highlights other more serious problem.
When doing any replacements, the codes must be reset to see if it comes back. Doing so will let you know if the problem is solved.