C1239: ABS Hydraulic Pressure Differential Switch Input Open Circuit
Methodology: Reviewed against the SAE J2012 generic DTC definition and NHTSA complaint patterns, then kept at generic code level because this page is not scoped to one make or model.
Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).
- SAE J2012 Diagnostic Trouble Code Definitions — Generic diagnostic trouble code definition reference for C1239.
- NHTSA recalls, complaints, and manufacturer communications — Used to check public complaint context, recall status, and safety-related manufacturer communications by VIN or vehicle.
Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.
What Does C1239 Mean?
C1239 code: ABS Hydraulic Pressure Differential Switch Input Open Circuit. Symptoms, likely causes, diagnostic path, severity, and repair cost context.
Symptoms of C1239
- ⚠️ Warning light or diagnostic trouble code is stored
- ⚠️ Symptoms vary by vehicle and by the system that set the code
- ⚠️ Related codes, freeze-frame data, and live data are needed before replacing parts
- ⚠️ Vehicle may fail an emissions or safety inspection until the code is resolved and monitors reset
Common Causes
- 🔍 Circuit, sensor, actuator, wiring, connector, module, or mechanical condition detected by the relevant control module
- 🔍 Low battery voltage, poor ground, corrosion, water intrusion, or intermittent connector contact
- 🔍 Vehicle-specific calibration or service bulletin condition that must be checked by VIN
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"For the past 2 years I've had issues with the ABS, Traction, and Brake lights coming off and on on my dashboard of my 2011 Toyota Prius. Mechanics have replaced various things but have never been able to find the exact problem because the car doesn't either give any codes or it gives codes that don'"
— Toyota Prius owner, 2024-08-01
Source: NHTSA Complaints Database
Most Reported Vehicles for C1239
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | TOYOTA PRIUS |
Frequently Asked Questions
Is C1239 enough to replace a part?
Can I drive with C1239?
What To Do Next
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1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.