Code Definition

C1238 — ABS Hydraulic Pressure Differential Switch Input Circuit Failure

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

About C1238

C1238 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 C1238 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

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.

C1238 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 C1238 sets when the ABS module detects an electrical fault in the input circuit from this switch, such as an open, short to ground, or short to voltage. The pressure differential switch is normally a simple two-wire device mounted in the proportioning valve assembly or master cylinder block, and it closes (or opens) when one circuit loses pressure relative to the other. When this code is set, the ...

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