P0593
UniversalCruise Control Multi-Function Input B Circuit High
Low SeverityThis code indicates that the Powertrain Control Module (PCM) has detected a voltage reading in the cruise control multi-function input B circuit that is higher than expected. This typically means there is an electrical fault preventing the cruise control system from receiving correct signals, which will disable the cruise control function.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before performing any electrical repairs to prevent accidental short circuits or electrical shock. Be cautious when working around airbags and their wiring, as improper handling can lead to accidental deployment. Ensure the vehicle is off and in park with the parking brake engaged before beginning any inspection or repair.
Common Symptoms
- Cruise control system is inoperative
- Check Engine Light illuminated
- Cruise control indicator light may not illuminate
Common Causes
- Faulty cruise control multi-function switch
- Short to voltage in the cruise control multi-function input B circuit wiring
- Corroded or loose electrical connectors
- Blown fuse related to the cruise control system
- Faulty Powertrain Control Module (PCM) (less common)
Frequently reported on: General/Universal
Diagnostic Steps
- Inspect all accessible wiring and connectors related to the cruise control system for signs of damage, corrosion, or looseness. Pay close attention to the cruise control switch itself.
- Check all fuses related to the cruise control system and the vehicle's electrical system, replacing any blown fuses.
- If possible, test the continuity and resistance of the cruise control multi-function switch using a multimeter. Refer to your vehicle's service manual for specific values.
- Clear the code and test drive the vehicle to see if the P0593 code returns. If it does, further electrical diagnosis will be required.
👨🔧 When to Call a Professional
While cruise control is not essential for vehicle operation, a persistent P0593 code warrants attention. You should consult a professional technician if you are uncomfortable diagnosing electrical circuits, or if initial DIY troubleshooting steps like checking fuses and connectors do not resolve the issue. Wiring harness issues or internal PCM problems require specialized diagnostic tools.
Commonly Asked Questions
What does 'Multi-Function Input B Circuit High' mean for my cruise control?
It means the vehicle's computer is seeing a higher than normal voltage in a specific part of the cruise control system's electrical circuit, which prevents it from working correctly.
Is it safe to drive with code P0593?
Yes, it is generally safe to drive with this code. It primarily affects the functionality of your cruise control, but does not impact critical vehicle operations like braking, steering, or engine performance.
Can a blown fuse cause a P0593 code?
Yes, a blown fuse in the cruise control circuit or related electrical systems can sometimes lead to this code. It's one of the first things to check during diagnosis.
How can I test the cruise control switch for P0593?
You can use a multimeter to check for proper voltage and resistance at the switch and its connectors. You'll need to consult your vehicle's specific wiring diagram and service manual for the correct testing procedures and values.
Will fixing the P0593 code automatically reset my Check Engine Light?
Once the underlying issue is repaired, the Check Engine Light may turn off on its own after several drive cycles. However, it's often best to clear the code with an OBD-II scanner to confirm the fix immediately.