ESC System Fault -- Reduced Function
What does C0240 mean?
The C0240 code means the vehicle's onboard diagnostic system has detected: ESC System Fault -- Reduced Function. This is a critical severity code.
Common Symptoms
- Stability control warning light on
- Traction control light on
- Service StabiliTrak or ESC message
- System operates in degraded mode
- Reduced stability assistance in emergency maneuvers
Probable Causes (Ranked by Likelihood)
- Multiple sensor faults reducing system capability Very High
- ABS module partially functional High
- Intermittent CAN bus communication errors Moderate
- Low battery voltage affecting module operation Moderate
- ESC module internal partial failure Low
Step-by-Step Diagnostic Procedure
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Scan for all DTCs in every module -- this code often accompanies other faults
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Check battery voltage and charging system health
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Monitor CAN bus for communication errors using a scan tool
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Address any companion codes first as they may be the root cause
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Check for software updates or TSBs for the ESC module
Frequently Asked Questions
What does reduced function mean for ESC?
The ESC system has detected a fault that prevents full operation but still has enough functional sensors and actuators to provide limited stability assistance. It is operating in a degraded mode with less capability.
Should I fix the other codes first?
Yes. C0240 is often a secondary code that appears when another fault reduces ESC capability. Fixing the primary fault -- such as a wheel speed sensor or steering angle sensor issue -- usually resolves this code as well.
Can a weak battery cause reduced ESC function?
Yes. The ESC system requires stable voltage to operate its sensors and solenoids. Low battery voltage or a failing alternator can cause the system to enter a reduced function mode.