P0129 - BAROMETRIC PRESSURE TOO LOW

POST UPDATED IN April, 2021

Description of DTC code P0129 Generic

DTC code P0129 OBD2 is stored because the Powertrain Control Module (PCM) has detected a barometric pressure reading below the set limit. This reading comes from the BPS (Barometric Pressure Sensor) or MAP (Manifold Absolute Pressure Sensor).

The BPS Sensor helps the PCM change to atmospheric pressure. This pressure is exactly related to the degree of altitude applied to the vehicle. The information obtained is used to calculate fuel delivery as well as ignition timing. Usually this sensor has a reference signal, a battery ground and an output signal circuit. In addition, this sensor completes the reference voltage circuit and delivers the necessary resistance as determined by the actual barometric pressure.

When there are changes in atmospheric pressure, the resistance levels of the BPS Sensor also react accordingly. This varying resistance in the sensor causes changes in the output voltage from the sensor to the PCM. In case the PCM finds an input signal from the BPS Sensor which varies from the programmed limit, this code will be stored.

Symptoms of fault code P0129 Generic

  • Illuminated Check Engine light.
  • Fuel delivery conditions are excessively rich.
  • The engine loses performance.
  • The engine hesitates during acceleration.
  • Lower fuel economy.
  • Excessive amount of black smoke escapes through the exhaust.

Causes of OBD2 P0129 Generic

The most likely causes for configuring diagnostic code P0129 OBDII are:

  • MAP or BPS Sensor connector may be corroded.
  • The motor may have worn out and there is insufficient vacuum.
  • Catalytic Converter may be clogged.
  • Maybe the BPS Sensor or MAP is defective.
  • Wiring for faulty MAP or BPS

Possible solutions of the DTC code P0129 Generic

The steps to give solution to the faults related to the fault code P0129 OBD2 are:

  • Check if there is TSB (Technical Service Bulletins) corresponding to the model of your vehicle.
  • Check all wiring harnesses and connectors that pertain to the system. Any of these damaged components should be repaired or replaced, delete the code.
  • In the event the code returns, perform a manual engine vacuum test to verify that the necessary vacuum is being made. Compare with vehicle information data for specifications.
  • Inspect the air filter. If it is dirty, it causes corrosion of the barometric pressure sensors.
  • Unplug the electrical connector of the BPS Sensor and check the resistance in all its circuits using a DVOM. If it does not meet the manufacturer's recommended specifications, it will need to be replaced.
  • If the sensor has no problem, test the system circuits. To do this, you must disconnect the controllers before testing to avoid damage. Repair or change open or shorted circuits.

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