C0240 critical

ESC System Fault -- Reduced Function

The C0240 code means the vehicle's onboard diagnostic system has detected: ESC System Fault -- Reduced Function. This is a critical severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $100 - $1500 (parts and labor)

Read ABS Codes

BlueDriver Bluetooth Pro Scanner

Basic scanners cannot read ABS codes. BlueDriver reads all systems including ABS, SRS, and transmission through your phone.

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Read ABS Codes

LAUNCH CRP123X (Reads ABS + Chassis)

Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.

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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

Scan for all DTCs in every module -- this code often accompanies other faults
Check battery voltage and charging system health
Monitor CAN bus for communication errors using a scan tool
Address any companion codes first as they may be the root cause
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.