Guide To P0129 OBD Error Code Solutions

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The barometric pressure sensor is designed to allow the PCM to record variations in atmospheric pressure. Atmospheric pressure is directly associated to the specific degree of altitude, as it is applicable to your car. The PCM retrieves and uses this data to assist with directing a strategy for fuel delivery and ignition timing.

The barometric pressure sensor is usually stored with a sourced voltage signal, a battery ground, and one (or multiple) output signal circuit(s). As atmospheric pressure changes occur, BPS resistance levels respond appropriately. The BPS holds resistance changes that create differences in the sensor output voltage being sent to the PCM. These changing voltage signals are not just used by the PCM to map fuel delivery and ignition timing strategy, but also collate to programmed identifications. If voltage signals fail to follow with the programmed designations, throughout a round course of time under particular conditions, a P0129 code with be supplied and a service engine lamp will soon be illuminating.

Since nearly each manufacturer uses a customized system of detecting barometric pressure, this kind of code can be misleading. Provided is a brief description of some of our most common designs. Noting, that this is not even close to being a all-inclusive list. Seek advice with your vehicle service manual, Mitchell on Demand, or All Data to find out the exact BPS design for
your car.

Some automakers use a BPS that is completely detached from the MAP sensor. It is typically mounted on the firewall or inner fender and connected to it is a vacuum hose. The engine intake vacuum comes to a degree as it collected by the sensor and input to the PCM, where it is collated with the input signal by the MAP sensor, intake air temperature and other factors to direct precise altitude (elevation above sea level). If the BPS input signal differs by more than a set limit, a P0129 will be supplied.

Other manufacturers decide to combine the BPS with the MAP sensor. According to this kind of system the sensor is usually mounted directly to the engine intake manifold and a certain kind of O-ring is sealed around it. Cars with this kind of system normally replaces the manifold air pressure for barometric pressure and the scanner data stream may demonstrate this terminology.

What causes this problem with the Barometric Pressure?

• Faulty MAP sensor
• Defective BPS
• MAP sensor and/or the BPS has open or shorted wiring
• Damaged connector face at the MAF/BPS sensor
• Deficient system ground at the MAF/BPS
• Faulty PCM or PCM programming glitch

1. Powertrain Control Module - PCM issues can affect the engine’s performance and can make the car return further to safe condition in order to stop future damages. It is smart to replace this failed PCM as early as possible.
2. Manifold Absolute Pressure Sensor - A defective MAP sensor will cause your car to fail an emissions test, where your tailpipe emissions may show a high level of hydrocarbons,
   high NOx production, low CO2, or a high level of carbon monoxide. Seek out a properly trained
   technician who is capable of diagnosing and repairing a defective MAP sensor.
3. Barometric Pressure Sensor - If the BAP sensor fails to function, it can send an inaccurate signal to the computer that might have a bad effect on engine performance, which may cause severe cases of slow acceleration, lack of power and misfires.
4. MAF sensor - If the MAP sensor reads too low, the situated computer will cut back the quantity of fuel it thinks is needed and starve the engine, causing it to run irregularly and reduce power.
   If your car has a defective manifold pressure sensor, find a qualified mechanic to perform complete engine diagnostics.
5. Intake Air Temperature Sensor - The computer of a damaged IAT sensor may send the wrong amount of fuel, interrupting the balance in the air-fuel mixture and causing a lot of driving problems by rich or lean mixtures. Avoid this by getting a new IAT sensor as soon as possible.
6. Timing Belt - The timing belts might snap and run into each other, resulting in belt valves, cylinder head or camshaft damage, and even tand cylinder wall damage. Find a certified technician or mechanic to check the timing belt and replace it if needed.

When you find a P0129 OBD code programmed in your equipped car, it means that the powertrain control module (PCM) has detected a low barometric pressure reading from the barometric pressure sensor (BPS) or the manifold absolute pressure sensor (MAP).

Common Symptoms

• Immoderate rich fuel delivery conditions
• Basic reduction of engine performance
• Pausing on speed capacity
• Exhaust emitting black smoke
• Decreasing fuel efficiency

The barometric pressure sensor is typically supplied with a reference voltage signal, a battery ground, and one (or more) output signal circuit(s). The BPS finishes the reference voltage circuit and gives the rightful resistance as determined by actual barometric pressure.

• Timing Belt Replacement
• MAP Sensor Replacement

A diagnostic scanner, a digital volt/ohmmeter, a vacuum gauge, and a vehicle service manual (or online service such as All Data or Mitchell On Demand) will be needed to accurately diagnose the OBD P0129 code error.

• I usually start my diagnosis with a visual checkup of any system equivalent wiring harnesses and connectors that I can gain full access to in a practical duration of time. Damaged wiring or corroded connector faces must be repair before ongoing process of diagnosis.
• Take this advantage to detect battery voltage capacity and alternator output. Detect battery terminal ends for immoderate damage. Clean and tighten terminal ends as needed. Undertaking this problem (currently) may be a time-saver if P0129 has been supplied because of a low battery voltage or voltage drop circumstance.
• The scanner connects to the diagnostic connector to receive all supplied codes. Take note of all codes and freeze frame data that day as this verifies the situation that you are faced with an irregular code.
• Execute an engine vacuum test to make sure that the engine is making enough vacuum. Inquire with the service manual or information service to grab a hold of identifications that are applicable to your car. Engines that are not functioning effectively will not create enough vacuum to the BPS or MAP sensor. Engine discharge codes should be diagnosed and fixed in advance while trying to diagnose this code. Conditions such as jammed catalytic converters, limited mufflers, and reduced fuel pressure may also play a part in losing engine vacuum.
• Speaking from my personal experience, barometric pressure sensors that are combined with the MAF sensor are by topic of corrosion at the connector face. These system types are by topic of function failuers lead by an immensely dirty air filter element. Furthermore, to these regular tendencies, this kind of BPS arrangement will frequently need a supplementary ground to be installed. Inquire with the service manual or information service for technical service bulletins that are applicable to the barometric pressure sensor, manifold air pressure sensor, or mass air flow sensor of your car.
• All circuits and connectors should appear in correct order, if so, press on examining with the MAP/BPS sensors. Inquire with the service manfual for precise identifications related to your car. The electrical connect has to be unpluged to detect for any resistance across all the circuits by using the DVOM. Exchange the sensor if it faulters to obey the identifications.
• If the sensor meets the automaker’s needs, start testing the system circuits. Ensure that system cource voltage and ground signals are in view. Disconnect all equivalent controllers to stop damage in advance, before testing system circuits with the DVOM. Fix or exchange open or shorted circuits as needed.
• If all sensors and circuits are inclined with automakers identifications, assume a faulty PCM or a PCM programming glitch. Take in mind all the automakers recalss and TSBs before exchanging and memorizing that replacing the system controllers will need reprogramming.

Common Mistakes When Diagnosing The P0129 Code

• Inlet Pressure Sensor failure
• Powertrain Control Module (PCM) defect
• Wiring problem