The Ford Auto Start-Stop system automatically shuts off the engine when the vehicle comes to a stop to save fuel. This system can improve fuel efficiency by 3-4 mpg in city driving. However, drivers may encounter issues with the system not activating as expected. Diagnosing the specific cause is key to restoring proper operation.
Problem Explanation
The key purpose of the Auto Start-Stop system is to cut engine run time for enhanced fuel savings. This is achieved by seamlessly shutting down the engine when the vehicle brakes to a stop, such as at a traffic light. Upon lifting your foot off the brake, the engine automatically restarts once you touch the accelerator.
When the Auto Start-Stop fails to perform this stop/start function, owners miss out on increased gas mileage. In heavy city driving conditions, malfunctions can reduce real-world economy by 5-12 mpg. With high fuel prices, this equals $350 or more in lost savings per year.
Determining the root cause requires methodical troubleshooting between the intricately connected powertrain and engine management components. Any degradation of the battery, sensor data, or mechanical issues can prevent the engine from shutting off or restarting. Electrical, drivetrain, and climate control systems must synchronize processes to enable the functionality.
Potential Causes
Environmental Factors
Frigid temperatures below 5°F or excessively hot temps above 110°F often exceed the Auto Start-Stop’s operational range. The system further disengages above approximately 10,000 feet altitude given oxygen sensor limitations. Programming manages appropriate engine run time and efficiency.
Vehicle Conditions
The Auto Start-Stop coordinates the battery, electrical control modules, powertrain, and HVAC systems. Insufficient battery charge below 58% disables the system as proper voltage ensures reliable restarting. Engine temperature, transmission oil temperature, or output issues also impact functioning.
Other Triggers
Steep uphill grades place extra load on the engine, making automatic shutdown problematic. Running accessories like rear defrosters and heated seats/steering wheels taps electrical power, signaling the system to remain active. Doors ajar or hood open can indicate service mode necessitating sustained operation as well.
Troubleshooting and Solutions
Basic Checks
Technicians first verify doors/hood closed, battery charge over 12.6V, and the Auto Start-Stop enabled in infotainment settings. Switching off all non-essential accessories eases electrical load during testing. They further check for recent service announcements related to the issue.
Specific Issues
Recharging or replacing an inadequate battery can cost $150-250. Operating the vehicle within the Auto Start-Stop’s 40°F to 105°F temperature range facilitates engagement. Consult Ford’s diagnostic chart for tailored solutions like cooling the transmission if overheated.
Advanced Diagnostics
Connection of a professional-grade scan tool pulls any fault codes stored for the Auto Start-Stop system or associated components. Specialty tools ping sensors and control units regarding voltages, resistance, temperature values, and processing speeds to isolate failure points. This pinpointed input facilitates parts replacements or software recalibrations to restore normal functioning.
Cost of Repairing This Issue
Minor repairs average $350 if sensors or control modules require replacement. Battery replacement with programming ranges from $200-300 including labor. More extensive mechanical issues involving the starter or transmission may cost up to $1,500.
Proper diagnostics minimizes guessing, avoids unnecessary parts expenditures, and reduces labor time. Maintaining Auto Start-Stop operation optimizes fuel efficiency, providing long-term savings.
John Smith, a Los Angeles-based car specialist and automotive writer, boasts over 20 years in the industry. With a background as a master technician and a decade-long writing stint at notable automotive publications, John now shares his expansive knowledge on CarFinite, simplifying car maintenance for readers.