BMW DTC P1240 – Secondary Upstream Manifold Air Pressure Sensor Signal Too Low at Idle Engine Running
DTC P1240 meaning on BMW
The DTC P1240 on a BMW indicates that the Secondary Upstream Manifold Air Pressure Sensor is sending a signal that is too low when the engine is idling.
BMW DTC P1240 symptoms
Some symptoms that may be experienced with the DTC P1240 on a BMW include:
- Check Engine Light illuminated
- Decreased engine performance
- Engine stalling at idle
BMW DTC P1240 causes
There are several potential causes for the DTC P1240 on a BMW, including:
- Faulty Secondary Upstream Manifold Air Pressure Sensor
- Wiring or connector issues in the sensor circuit
- Vacuum leaks in the intake system
BMW DTC P1240 seriousness
The DTC P1240 should be addressed promptly as it can lead to poor engine performance and potential stalling, which can be dangerous while driving.
How to diagnose DTC P1240 on BMW
To diagnose the DTC P1240 on a BMW, a mechanic would typically perform the following steps:
- Use a diagnostic scanner to retrieve the fault code
- Inspect the Secondary Upstream Manifold Air Pressure Sensor and its wiring for any visible damage
- Check for vacuum leaks in the intake system
How to fix DTC P1240 on BMW
To fix the DTC P1240 on a BMW, the following steps may be taken:
- Replace the faulty Secondary Upstream Manifold Air Pressure Sensor
- Repair any damaged wiring or connectors in the sensor circuit
- Address any vacuum leaks in the intake system
How to erase DTC P1240 on BMW
After the issue causing the DTC P1240 on a BMW has been resolved, the fault code can be cleared using a diagnostic scanner to erase the code from the vehicle’s memory.
Recommended tools & DTC Scanners for BMW
Best Diagnostic App for modern BMWs: BimmerLink
Recommended Bluetooth adapter for Bimmerlink: OBDLink CX
Cable adapter for Bimmerlink: Enet Cable USB Type C
For older BMWs we recommend: Autel AutoLink AL319 (2024 version)
Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter
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