ABS Code C1240: Pressure Switch Short to Battery
Diagnostic trouble code C1240 indicates that the ABS control module has detected a short circuit to battery positive voltage in the input circuit of the hydraulic pressure differential switch. This switch monitors brake hydraulic pressure; a voltage signal above the calibrated threshold suggests a fault in the wiring, connector, or the switch itself, preventing accurate pressure readings and disabling the ABS system.
1. Commonly Affected Makes
2. Most Common Causes
- Short to battery voltage in the hydraulic pressure switch wiring harness
- Defective hydraulic pressure differential switch (internal short)
- Damaged, corroded, or bent pins in the switch connector
- Internal failure of the ABS control module (input driver circuit)
3. Symptoms You Will Notice
- ABS warning light illuminated on the dashboard
- ABS system disabled; normal braking remains but without ABS function
4. Step-by-Step Diagnosis
Scan for additional ABS codes and record freeze frame data
Visually inspect the hydraulic pressure switch connector and wiring for damage, corrosion, or shorts to battery voltage
Measure voltage at the switch signal wire with ignition on; compare to manufacturer specifications
Test the switch by disconnecting it and checking for continuity/resistance per service manual
If wiring and switch are okay, suspect a faulty ABS module and perform further module diagnostics
5. Frequently Asked Questions
Is it safe to drive?▼
Driving is not recommended because the ABS system is disabled, increasing the risk of wheel lockup during hard braking, especially on slippery surfaces. Have the vehicle repaired as soon as possible.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on whether the issue is a simple wiring repair, a switch replacement ($50–$200), or an ABS module replacement ($300–$600).