Code C1240 indicates the ABS control module has detected a short to battery voltage on the signal circuit for the hydraulic pressure differential switch. This switch monitors brake pressure balance between circuits; a short to power can cause false readings, potentially disabling ABS and traction control functions.
Chafed, pinched, or melted insulation on the pressure differential switch signal wire allows contact with a 12V power source, causing a constant high voltage reading.
Internal short circuit within the switch itself can cause the signal line to be pulled up to battery voltage, mimicking a wiring short.
Moisture intrusion, bent pins, or corrosion at the switch or ABS module connector can create a conductive path to a power source.
In some designs, the pressure differential switch is integrated into the hydraulic assembly; an internal fault can cause a short to battery voltage.
An internal short in the module's input circuit is possible but rare; this should be considered only after all external wiring and the switch are verified good.
It means the ABS control module has detected a short to battery voltage on the circuit for the hydraulic pressure differential switch. This switch monitors brake pressure balance, and a short can cause false readings or system disablement.
The vehicle may still have normal braking, but the ABS and possibly traction control systems may be disabled. This can increase stopping distances in slippery conditions, so drive cautiously and have the issue diagnosed promptly.
No. The most common causes are a shorted wire in the harness or a faulty pressure differential switch. Replacing the ABS module without checking the wiring and switch often does not fix the problem.
Extremely unlikely. The code is set by the ABS control module based on its own circuit monitoring. The PCM is not involved in this diagnostic; focus on the ABS module, switch, and wiring.