Error Code P0129: All You Need to Know

The pressure is real when it comes to the error code P0129. The low barometric pressure error can trouble you, especially during a high-altitude journey. Does this occur in normal altitudes? What are the symptoms and how do we fix them? Read everything you need to know about the error code P0129 here. 

What does the P0129 code mean?

The error code P0129 denotes that the barometric pressure is too low. This occurs when the power train control module (PCM) detects a pressure lower than that specified by the manufacturer. In other words, the P0129 error code occurs when there is trouble with either the manifold air pressure (MAP) sensor or the barometric air pressure (BAP) sensor.

PCM and the BAP sensor

The atmospheric pressure is directly proportional to the altitude. The barometric air pressure (BAP) sensor enables the PCM to track variations in air pressure. The PCM uses the information given by the BAP to calculate how much fuel to give and when to start the engine.

Furthermore, a reference voltage signal, a battery ground, and one or more output signal circuits are sent to the barometric pressure sensor. The BPS completes the circuit for the reference voltage and gives the right amount of resistance based on the actual barometric pressure.

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When your car is at a relatively higher altitude, the atmospheric pressure automatically changes so do the BPS resistance levels followed by the voltage that the sensor sends to the PCM. As a result, the PCM compares them to the parameters that were programmed to store the code. Therefore, when the PCM perceives that the voltage signal from the sensor is too low, it will trigger the P0129 code.

What causes error code P0129?

The common causes of P0129 are as follows:

• Defect in the manifold air pressure sensor
• Faulty barometric air pressure sensor
• Issues in the wiring or connectors
• Corrosion in the connector face at either of the sensors
• Error with PCM
• Clogged catalytic converter
• System ground deficiency at the sensors

What are the symptoms of the P0129 code?

One can suspect this error code if you come across the following symptoms.

• Check engine light is activated
• High fuel consumption
• Poor engine performance
• Engine misfire
• Engine hesitation while accelerating
• Exhaust emitting black smoke

How serious is this code?

Since engine misfires and exhaust gases invading the car interiors can occur due to this, it is important to fix it as soon as you start witnessing the symptoms mentioned above.

How do you diagnose and fix the error code P0129?

There is no single solution to a P0129 code. The specifications of BAP and MAP sensors can differ greatly between car manufacturers. For instance, the methods for correcting a P0129 issue on a Hyundai model may not apply to a Lexus model.

A scanner, a digital volt/ohmmeter, and a vacuum gauge are required to diagnose the error. Following the steps below will certainly help you navigate through the diagnosis and the recommended repair procedure.

• Visual inspection for damaged wiring and connectors. You must repair them if damaged, before proceeding with the rest of the diagnosis.
• Since a low battery voltage can contribute to the P0129 error, check the battery voltage capacity and the terminal ends.
• Take notes for all codes to ensure that the fault lies only with the mentioned sensors and system not anything else.
• Carry out an engine vacuum test. However, fixing the engine discharge codes before this as jammed catalytic converters, limited mufflers, and reduced fuel pressure may also play a part in losing the engine vacuum.
• Assume a faulty PCM or a PCM programming glitch if all sensors and circuits are inclined with the maker’s specifications.
• Any damage detected with the wiring and connectors must be repaired.

Also Read: All You Need to Know About OBD 2 Scanner

How much does it cost to fix error code P0129?

Detecting the P0129 error code is a laborious process. Therefore, it will cost in the range of $75 and $150 per hour, although the labor charge can vary with the place and the make of the car.

Can you fix the code yourself?

It is always better to seek professional help since a certain level of technical knowledge is required to fix the issue. This is also because the error code is sometimes accompanied by a host of other trouble codes. However, you can always run a diagnosis if you face any of the symptoms and seek early help.

 

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