P129B – BMW DTC

BMW DTC P129B – Manifold Absolute Pressure Sensor ‘A’ Afterrunning Diagnosis Pressure Implausible

DTC P129B meaning on BMW

The DTC P129B on a BMW indicates an issue with the Manifold Absolute Pressure (MAP) Sensor ‘A’ after running diagnosis pressure being implausible. This means that the pressure reading detected by the MAP sensor is not within the expected range after the engine has been running.

BMW DTC P129B symptoms

Symptoms of the DTC P129B on a BMW may include:

• Check Engine Light (CEL) illuminated on the dashboard
• Decreased engine performance
• Engine stalling or rough idling
• Poor fuel efficiency

BMW DTC P129B causes

Common causes of the DTC P129B on a BMW include:

• Faulty MAP sensor
• Vacuum leaks in the intake system
• Wiring or connector issues related to the MAP sensor
• Issues with the intake manifold

BMW DTC P129B seriousness

The DTC P129B should not be ignored as it can lead to poor engine performance and potentially cause further damage if not addressed promptly. It is recommended to diagnose and fix the issue as soon as possible.

How to diagnose DTC P129B on BMW

To diagnose the DTC P129B on a BMW, you can perform the following steps:

1. Use a diagnostic scanner to retrieve the fault codes and check for the P129B code.
2. Inspect the MAP sensor and its wiring for any visible damage or loose connections.
3. Check for vacuum leaks in the intake system using a smoke machine or by visually inspecting the hoses.
4. Test the MAP sensor’s output voltage using a multimeter to ensure it is within specifications.

How to fix DTC P129B on BMW

To fix the DTC P129B on a BMW, you can try the following solutions:

1. Replace the faulty MAP sensor with a new one.
2. Repair any damaged wiring or connectors related to the MAP sensor.
3. Fix any vacuum leaks in the intake system by replacing the affected hoses or gaskets.
4. Clean or replace the intake manifold if necessary.

How to erase DTC P129B on BMW

To erase the DTC P129B on a BMW, you can use a diagnostic scanner to clear the fault codes stored in the vehicle’s ECU. Once the codes are cleared, you can drive the car and monitor if the issue reoccurs. If the problem persists, further diagnosis and repairs may be required.

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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