P1240
WysokiSensor Power Supply Malfunction — the engine sensor power supply system reported incorrect voltage or signal loss.
OBD-II (EN): Sensor Power Supply Malfunction
Code P1240 signals a problem with the engine sensor power supply — the controller detected incorrect voltage on the 5V reference line. The cause could be a faulty sensor, an open or short circuit in the wiring harness, or in rare cases, a fault in the controller itself (ECU). Due to the impact on the operation of multiple sensors simultaneously, prompt workshop diagnosis is recommended.
Symptoms
- Check Engine Light (MIL) on - Possible difficulty starting or unstable engine idle - Incorrect sensor readings (MAP, TPS, other 5V) - Possible engine entering limp mode - Deterioration of performance and fuel consumption
Possible causes
- Faulty or intermittent 5V reference power wire for sensors - Short circuit in the sensor power supply circuit to ground or battery voltage - Faulty sensor drawing excessive current and overloading the reference line - Internal fault in the controller (ECU/ECM) — damaged 5V regulator - Corrosion or oxidation of sensor harness connectors
Affected systems
Does code P1240 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.