Cruise Control Servo Control Circuit High
Code P0596 indicates the cruise control servo control circuit is reading a voltage that is too high. This prevents the cruise control system from functioning properly and may cause the vehicle to maintain an unintended speed or disable cruise control entirely.
What You Might Notice
- Cruise control inoperative or disabled
- Erratic cruise control operation
- Vehicle speed cannot be controlled with cruise control
- Check Engine Light illuminated
- Difficulty maintaining set cruise speed
Most Common Causes
- 1
Faulty cruise control servo motor
The servo motor may be failing or producing excessive voltage signals, causing the circuit to read high voltage at the ECM.
- 2
Wiring harness damage or short to power
Damaged wiring in the cruise control servo circuit or accidental short to battery voltage can cause high voltage readings.
- 3
ECM connector or terminal corrosion
Corroded or loose connections at the ECM can cause intermittent high voltage signals or improper signal interpretation.
- 4
Defective cruise control module or ECM
A malfunctioning engine control module may incorrectly interpret servo signals or have internal electrical faults causing high circuit voltage.
How to Diagnose It
- 1
Check Faulty cruise control servo motor — The servo motor may be failing or producing excessive voltage signals, causing the circuit to read high voltage at the ECM.
- 2
Check Wiring harness damage or short to power — Damaged wiring in the cruise control servo circuit or accidental short to battery voltage can cause high voltage readings.
- 3
Check ECM connector or terminal corrosion — Corroded or loose connections at the ECM can cause intermittent high voltage signals or improper signal interpretation.
- 4
Check Defective cruise control module or ECM — A malfunctioning engine control module may incorrectly interpret servo signals or have internal electrical faults causing high circuit voltage.
How to Fix It
- 1
Test and replace cruise control servo motor
Use a multimeter to test the servo motor voltage output and resistance values. If readings are abnormally high, replace the servo motor assembly.
- 2
Inspect and repair wiring harness
Visually inspect all cruise control servo wiring for damage, corrosion, or exposed wire. Repair or replace damaged sections and ensure proper connections to the ECM.
- 3
Clean and inspect ECM connectors
Disconnect the ECM connectors and clean all pins and terminals with electrical contact cleaner. Reconnect firmly and ensure all connections are tight and corrosion-free.
- 4
Test or replace ECM if fault persists
If all wiring and servo components test normal, the ECM may have internal faults. Have the module tested by a specialist or replaced if defective.
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