P0596

Code

Generic P — Powertrain

Cruise Control Servo Control Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 27 EN: 40 RU: 26

AI status

Completed

ready

Completed 100%

Page language: EN

Retrieve freeze frame data and monitor live data for cruise control status and related voltage/inputs
Visual inspection of cruise servo/actuator connector and harness for damage, corrosion, or pin push-out
Check battery and charging system voltage to rule out overall over-voltage condition
Backprobe/control-pin voltage at the servo connector with key ON (engine OFF) and while attempting to operate cruise
Inspect and verify integrity of ground(s) for the servo and ECM
Measure continuity/resistance between the ECM control pin and the servo connector pin with harness disconnected

Expected: control circuit voltage within manufacturer-specified range (typically low-voltage control or PWM; consult factory manual for exact values)
Fault condition: control circuit voltage higher than allowed threshold (may be near battery voltage or above expected PWM amplitude)
Key ON engine OFF: control output should follow specified idle state (often low or specific PWM); a steady high/B+ is abnormal
When testing, use a digital multimeter for DC checks and an oscilloscope to inspect PWM or switching waveform if available

Connect a scan tool, read and record P0596 and any related codes and freeze frame data.
Visually inspect the cruise servo/actuator, wiring harness, and connector for damage, corrosion, or aftermarket splices.
Check vehicle battery and charging system voltage for over-voltage condition; correct if present and retest.
With ignition ON (engine OFF), backprobe the servo control pin and measure voltage. Compare to factory spec. Note if voltage is near battery voltage (indicating short to B+).
Disconnect the servo connector and measure voltage at the harness female terminal; if voltage remains high with servo disconnected, suspect wiring short or ECM output fault.
Check continuity between the control pin at the harness and the ECM pin. Also check continuity to chassis ground and verify ground resistance is low.
Wiggle the harness and connector while monitoring the circuit for intermittent changes. Repair any damaged wiring or corroded connectors.
If wiring and grounds are good, bench-test or replace the cruise servo/actuator. If a known-good servo resolves the problem, replace the failed unit.
If a replacement servo does not clear the fault and wiring checks good, suspect ECM driver fault; verify with manufacturer procedures before replacing ECM.
After repairs, clear codes, perform a functional test of cruise control and road test to confirm the repair.

Wiring shorted to B+ at or near the servo connector
Open or high resistance ground(s) causing abnormal voltage readings
Internal failure in the cruise servo causing the control output to read high
Connector corrosion or pins pushed out of connector causing intermittent high voltage