C1240
WysokiInput Short – ABS Hydraulic Pressure Differential Switch Short to Battery.
Fault code C1240 indicates a short circuit in the ABS pressure differential switch circuit, which can lead to the deactivation of safety systems such as ABS and ESP. The most common cause is damaged wire insulation or a faulty sensor. We recommend contacting a workshop as soon as possible for professional diagnosis.
Symptoms
ABS warning light illuminated on the dashboard. Possible deactivation of ABS and Electronic Stability Program (ESP). During hard braking, loss of braking force modulation, increased stopping distance, and wheel lockup may occur. In some cases, the brake system warning light may also illuminate.
Possible causes
Short circuit of the pressure differential switch signal wire to the positive battery terminal (e.g., chafed insulation). Internal damage to the pressure differential switch (short circuit). Corrosion or moisture in the connector of the pressure differential switch wire. Faulty ABS/ESP control module (less common).
Affected systems
Sources and further reading
Does code C1240 require professional diagnostics?
The code alone is not enough. To find the cause, you need to read live data, check freeze frame conditions, and compare with vehicle behavior. Book a diagnostic session.