Cruise Control Cannot Hold Speed
The P1575 code is a manufacturer-specific diagnostic trouble code indicating that the Powertrain Control Module (PCM) has detected the cruise control system is unable to maintain the driver's set speed. During cruise control operation, the PCM monitors actual vehicle speed and compares it to the programmed target. If the actuator or regulating mechanism fails to compensate for load or resistance changes, causing the speed to persistently drop below the desired value, this fault is recorded. It reflects the system's inability to adjust engine power sufficiently to sustain a constant speed.
01. Most Common Causes
- Faulty cruise control servo or vacuum leak (in systems with a pneumatic actuator)
- Sticking, misadjusted, or damaged throttle cable or cruise control cable
- Deteriorated, disconnected, or broken vacuum hoses supplying the servo
- Open, shorted, or high-resistance wiring or connectors between the servo, switches, and PCM
- Corroded or worn cruise control switch contacts (SET/RESUME/COAST)
- Internal PCM failure or incorrect cruise control system calibration
02. Symptoms You Will Notice
- Cruise control engages but cannot maintain set speed, vehicle slows down
- Cruise control disengages unexpectedly or fails to activate
03. Step-by-Step Diagnosis
Check for vacuum leaks at the servo and vacuum hoses; repair or replace as needed
Inspect throttle and cruise control cables for binding, damage, or improper adjustment
Test cruise control switches for continuity and proper operation
Examine wiring and connectors between servo, switches, and PCM for damage or corrosion
If all else is OK, test the servo and PCM per manufacturer procedures
1. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive without cruise control. The vehicle's normal braking and acceleration are unaffected.
How much does it cost to fix?▼
Repair costs vary widely, typically ranging from $100 to $400 depending on the cause (e.g., vacuum hose replacement vs. servo replacement).