C1240: ABS Hydraulic Pressure Differential Switch Input Short Circuit To Battery
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 C1240.
- 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 C1240 Mean?
C1240 code: ABS Hydraulic Pressure Differential Switch Input Short Circuit To Battery. Symptoms, likely causes, diagnostic path, severity, and repair cost.
Symptoms of C1240
- ⚠️ 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.
"TL* THE CONTACT OWNS A 2009 TOYOTA PRIUS. THE CONTACT STATED THAT A WARNING INDICATOR FLASHED ON THE INSTRUMENT PANEL REGARDING THE BRAKE SYSTEM WHEN THE BRAKE PEDAL WAS DEPRESSED. THE CONTACT ALSO NOTICED SMOKE COMING FROM THE EXHAUST SYSTEM. THE CONTACT INSPECTED THE VEHICLE AND FOUND A LEAK UNDER"
— Toyota Prius owner, 2018-09-15
Source: NHTSA Complaints Database
Most Reported Vehicles for C1240
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | TOYOTA PRIUS |
Frequently Asked Questions
Is C1240 enough to replace a part?
Can I drive with C1240?
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.