Code Definition

C1240 — ABS Hydraulic Pressure Differential Switch Input Short Circuit To Battery

System: Chassis  |  Type: Manufacturer-Specific  |  Make: Generic

About C1240

C1240 is a manufacturer-specific chassis diagnostic trouble code. It belongs to the C-prefix family of codes, which covers chassis, braking, steering, suspension, or stability-control faults.

When C1240 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

Scanning & clearing: Chassis (C) codes are stored in the ABS, traction control, or stability-control modules. An enhanced or OEM-level scan tool is usually required to read and clear them.

C1240 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The ABS module monitors a hydraulic pressure differential switch that detects an imbalance in brake fluid pressure between the front and rear (or diagonal) hydraulic circuits of the brake system. DTC C1240 sets when the ABS module detects that the input signal wire from this switch has shorted to battery voltage, causing the input to read high regardless of the switch state. The pressure differential switch is normally a two-wire device mounted in the proportioning valve assembly or master cylinder block. When this code is set, the ABS module cannot trust the switch input, the BRAKE warning la...

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