P0594 - OBD Trouble Code

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The error code P0594 can be identified as Cruise Control Servo Control Circuit /Open. This trouble 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.

The P0594 fault code would start appearing if there is a problem with the cruise control circuit. Now if the powertrain control module would detect an issue with the cruise control, then it will run a self-instituted test of the system. If the voltage/resistance level would give an abnormal result within the cruise control servo control circuit, then it would start triggering up the P0594 error code.

What causes this problem with the Cruise Control Servo Control Circuit /Open?

• Problems related to wiring
• Faults in the engine control module
• Quirks in the connector
• Issue of module water intrusion
• The cruise control servo might have some defects
• There can be broken/stuck/disconnected/mis-adjusted cruise control servo cable

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2. Powertrain Control Module - A broken Powertrain Control Module can cause a lot of issues. It would be nice if you get it replaced on time.
3. Cruise Control Switch - Everything is fine with the engine control module and still OBD code P0594 flashing? Then there is definitely some fault with the Cruise Control Switch. Get it checked and replace if needed.
4. Cruise Control Relay - Cruise Control Relay is an important car part which should never be neglected. May be there is some fault in it due to which P0594 code may start flashing.
5. Throttle Position Sensor - A faulty Throttle Position Sensor can be troublesome. You can always rely on us as we have best auto parts for our customers.
6. Coolant Temperature Sensor - If everything is alright with PCM, then there is surely some defect in Coolant Temperature Sensor. Get it replaced before the situation gets worse.

Our main motive is to achieve customer satisfaction as for us our customers are everything and that’s why we will help you to diagnose P0594 code by mentioning some major symptoms below:

Common Symptoms

• Inaccurate vehicle speed setting when compared to desired or set speed
• Malfunctioning/erratic specific cruise control functions
• Cruise control inoperative
• The cruise control operation might be erratic
• Vehicle speed stuck
• Vehicle speed might be limited with cruise control active

If you wish to correct this fault code, then you have to follow certain steps. Correcting a problem needs your careful attention. Here are some ways with the help of which you will be able to correct the OBD Code P0594:

• First of all, you must verify the code with an OBD-II scanner
• Carefully inspect and repair the electrical components related to the cruise control servo control system
• Clear the code and perform a road test to ensure that the repairs solved the issue
• Check and replace any vacuum supply hoses in a vacuum operated cruise control system
• Disconnect the PCM, then inspect and test all wiring and switches in the cruise control system. Repair damaged circuitry as necessary
• The cruise control switches should be replaced properly

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Here are some steps which you should follow in order to diagnose this fault code:

Initial step in the troubleshooting process for any malfunction is to research the technical service bulletins for known issues with the specific vehicle. Advanced diagnostic steps become very vehicle specific and may require the appropriate advanced equipment and knowledge to perform accurately. We include basic steps below but refer to a vehicle year/make/model/powertrain specific repair guide for specific steps for your vehicle

Step 1

The cruise control servos are mounted in the engine compartment somewhere. Most times, they are in close proximity to the throttle body, after all they do control vehicle speed using this. Now once it is located, you must do a general visual inspection. Look at the cable, check for fraying, kinks, corrosion or any signs of malfunctioning. If the servo cable does not move freely when controlling the throttle, the ECM could interpret it as a performance issue

It's important to check all the vacuum lines running to the servo itself. Any cracked or deteriorated lines should be taken as a sign of your vacuum system's health so it is recommended to replace all of the vacuum lines involved as they are inexpensive and could save you from problems in the future

Step 2

On to the electrical side of things, verify the connector on the servo. Any broken tabs or loose connections should be repaired. The harness may be running through tight areas and/or moving parts, so be aware of any chafing areas that could cause an issue and repair any broken/ damaged wires

Step 3

Depending on your OBD2 scan tool capabilities, you can potentially monitor the servo's operation with it connected to the vehicle. Sometimes you may be given percentages or maybe electrical values. Either way you can compare the values to its physical operation by watching it under the hood, with the wheels off the ground

This is an old procedure and may cause issues especially when talking about more modern vehicles. That is the reason why you must always ensure any diagnosing/ repair procedures which are recommended by your vehicle's manufacturer. If you neglect to do your research here, you could easily damage other vehicle components

Common Mistakes When Diagnosing The P0594 Code

• While the P0594 trouble code is being diagnosed, then the most mistake which is made by a lot of mechanics is that they forget to disconnect the PCM and the cruise control module when testing circuit resistance
• It is very important to clear the code and do a proper road test
• If even the common repairs do not stop the check engine Light from reappearing, then it can be a sign of an intermittent issue that requires an in-depth inspection and servicing