Code Definition

C1239 — ABS Hydraulic Pressure Differential Switch Input Open Circuit

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

About C1239

C1239 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 C1239 is stored, the module has detected an open (broken or disconnected) electrical path 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.

C1239 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 C1239 sets specifically when the ABS module detects an open circuit condition in the input wiring from this switch, meaning the signal voltage is floating at the module input with no return path through the switch contacts. 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 canno...

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