Cruise Control Multi-Function Input Circuit High
The P0593 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the cruise control multi-function input circuit. This circuit typically carries signals from the cruise control switches (set, resume, cancel) to the PCM. A high voltage reading suggests a short to power, a faulty switch, or a wiring issue. This can disable the cruise control system and may affect other functions if the circuit is shared.
1. Most Common Causes
- Short to voltage in the cruise control switch circuit
- Faulty cruise control switch assembly
- Damaged wiring or connector in the cruise control circuit
- Corroded or loose electrical connections
- Faulty PCM (rare)
2. Symptoms You Will Notice
- Cruise control inoperative
- Cruise control light on dash may flash or stay on
- Engine Check Light illuminated
- Cruise control may engage but not disengage properly
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for other related codes.
Step 2: Visually inspect the cruise control switch wiring and connectors for damage, corrosion, or shorts.
Step 3: Test the cruise control switch circuit voltage with a multimeter; compare to manufacturer specifications.
Step 4: If voltage is high, disconnect the switch and recheck; if voltage drops, replace the switch.
Step 5: If voltage remains high, repair the short to power in the wiring harness.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, it is generally safe to drive, but cruise control will be disabled. If the circuit is shared with other critical functions, it could affect drivability. Have it diagnosed soon.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, depending on the cause. A switch replacement is around $50-$100, while wiring repairs may cost more.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.