Code
P0595
Generic
P — Powertrain
Cruise Control Servo Control Circuit Low
Views:
UK: 13
EN: 12
RU: 9
AI status
Completed
Completed
100%
Causes
- Blown fuse or faulty cruise relay (power supply interrupted)
- Open or high-resistance wiring in power or control circuit
- Short to ground on the servo control/conductor
- Poor or corroded connector or ground at the cruise servo
- Defective cruise control servo/actuator
- Faulty PCM/BCM or internal driver fault
Symptoms
- Cruise control will not engage or will drop out
- Cruise set/resume functions inoperative or intermittent
- Malfunction Indicator Lamp (MIL) or dash warning stored
- Possible abnormal actuator noises if partially powered
- No response when cruise switches are used
What to check
- Scan for stored codes and freeze-frame data; note related codes (brake switch, vehicle speed sensors, supply voltage codes)
- Visually inspect fuses, relays, connectors, and wiring for damage or corrosion
- Back-probe the cruise servo connector to check supply and ground with ignition ON
- Activate cruise switch (or simulate request) and observe control signal while monitoring voltage or waveform
- Wiggle wiring harness and connectors while monitoring for intermittent changes
- Measure continuity and resistance of wiring between PCM and servo; check grounds to chassis and battery negative
Signal parameters
- Supply voltage to cruise servo: near battery voltage with ignition ON (approx. 11–14 V) — verify against vehicle spec
- Control line: typically a switched or PWM-style signal from the PCM; expected amplitude normally between 0 V and battery voltage depending on duty cycle
- Ground: low resistance connection to chassis/battery negative (near 0 Ω continuity)
- Actuator coil/driver resistance: vehicle-specific — consult service manual (commonly low ohm range; if open/infinite or shorted to ground, actuator is faulty)
Diagnostic algorithm
- Retrieve all DTCs and freeze-frame data; check for related codes (e.g., supply voltage, brake switch). Note when the fault occurs (key on, while driving, when engaging cruise).
- Perform a visual inspection of fuses/relays for the cruise system and replace any blown fuses. Inspect connectors at the servo and PCM for corrosion, bent pins or water intrusion.
- Back-probe the cruise servo connector. With ignition ON (engine off) verify the supply pin reads battery voltage. If supply is absent, trace back to fuse/relay and ignition feed.
- With a helper operate the cruise switch (or simulate cruise request) while monitoring the control pin. Expect the control voltage or PWM duty to change when the system requests actuation. If the control line stays low, suspect wiring or the PCM driver.
- Check ground continuity from the servo ground pin to battery negative; repair any corrosion or high-resistance ground.
- Measure resistance of the actuator/servo (if service info available). An open or shorted actuator requires replacement. If resistance is within spec but actuator does not respond when commanded and wiring is good, suspect actuator electronics.
Likely causes
- Blown fuse or loss of supply voltage to cruise servo
- Poor ground or corroded connector at the servo
- Damaged control wire (short to ground or open)
- Failed cruise control servo/actuator
- PCM/BCM driver failure (less common)
Fault status
Status
Cruise control servo control circuit voltage low (control line below expected level).
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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