Cruise Control Servo Control Circuit Low
P0595 indicates the cruise control servo control circuit is reading a low voltage signal. The ECM has detected that the servo motor circuit is not receiving adequate electrical power or the signal is below the expected threshold, preventing proper cruise control operation.
What You Might Notice
- Cruise control inoperative or won't engage
- Erratic or unstable cruise control operation
- Vehicle speed fluctuates when cruise control is active
- Check Engine light illuminated
- Cruise control button unresponsive
Most Common Causes
- 1
Defective cruise control servo motor
The servo motor itself may be failing or have internal electrical faults, causing insufficient voltage draw or signal output to the ECM.
- 2
Wiring harness damage or corrosion
Corroded, frayed, or broken wiring between the servo and ECM can cause low voltage signals or complete circuit failure.
- 3
Faulty cruise control relay or connector
A failed relay or loose/corroded connector can reduce power delivery to the servo circuit, resulting in low voltage detection.
- 4
ECM or module programming issues
Outdated or corrupted ECM software may misinterpret servo signals, though this is less common than hardware faults.
How to Diagnose It
- 1
Check Defective cruise control servo motor — The servo motor itself may be failing or have internal electrical faults, causing insufficient voltage draw or signal output to the ECM.
- 2
Check Wiring harness damage or corrosion — Corroded, frayed, or broken wiring between the servo and ECM can cause low voltage signals or complete circuit failure.
- 3
Check Faulty cruise control relay or connector — A failed relay or loose/corroded connector can reduce power delivery to the servo circuit, resulting in low voltage detection.
- 4
Check ECM or module programming issues — Outdated or corrupted ECM software may misinterpret servo signals, though this is less common than hardware faults.
How to Fix It
- 1
Test and replace cruise control servo
Use a multimeter to verify servo motor voltage and resistance. If out of spec, replace the servo motor assembly with an OEM or quality replacement unit.
- 2
Inspect and repair wiring harness
Check the entire cruise control wiring harness for corrosion, damage, or loose connections. Repair, re-route, or replace damaged sections as needed.
- 3
Replace cruise control relay
Inspect the relay for signs of failure and test with a multimeter. Replace if resistance or continuity is abnormal, as a failed relay cannot supply proper voltage to the servo.
- 4
Scan and clear code after repairs
Use an OBD-II scanner to verify the code is resolved after completing repairs. Clear the fault code and test cruise control operation on the road to confirm the fix.
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