C1239 Code: ABS Hydraulic Pressure Differential Switch Input Open Circuit
🟠 Moderate severity · drivable
Drivable — standard brakes still work — but ABS may be disabled, so drive cautiously and fix it soon.
What C1239 means
The ABS hydraulic pressure differential switch input circuit is open, so the switch signal isn't reaching the ABS module.
Symptoms
- ABS warning light on
- ABS disabled (no pulsing during hard stops)
Common causes
- most common: Open wiring in the switch circuit
- common: Faulty pressure differential switch
- less common: Loose connector
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Repair open switch wiring | Mechanic | $50–150 |
| Replace the ABS hydraulic unit | Mechanic | $400–1200 |
Frequently asked questions
Can I drive with a C1239 code?
Yes, regular brakes still work, but ABS may be disabled. Drive cautiously.
What is the most common cause of C1239?
Open wiring in the pressure switch circuit.
How much does it cost to fix a C1239?
$50–$150 for wiring, or $400–$1,200 for a hydraulic unit.
Related codes
C1238
C1238 Code: ABS Hydraulic Pressure Differential Switch Input Circuit Failure
C1100C1100 Code: ABS Pump Switch Circuit Failure
C1096C1096 Code: ABS Hydraulic Pump Motor Circuit Open
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.