P0129 indicates that the engine control module has detected a barometric pressure reading that is lower than expected. This usually points to a problem with the manifold absolute pressure (MAP) sensor, its wiring, or an intake leak causing unusually low manifold pressure.
The MAP sensor may be stuck low or output an incorrect voltage, causing the PCM to interpret barometric pressure as too low.
Damaged, corroded, or loose wires and connectors in the MAP sensor circuit can produce a false low signal.
Leaks in hoses, gaskets, or the intake manifold allow extra air in, lowering manifold pressure and triggering the code.
Some vehicles use a dedicated barometric pressure sensor; a failure here can send a low pressure signal to the PCM.
Although rare, a defective powertrain control module could misinterpret sensor data; this should be considered only after other causes are ruled out.
The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:
No. PCM failure is an uncommon cause of P0129; most cases are due to the MAP sensor, its wiring, or an intake leak. Replace the PCM only after those components have been verified as functional.
Driving is possible but may result in reduced power, poor fuel economy, and increased emissions. Prolonged operation with a faulty MAP sensor can also affect engine performance and catalyst health.
Cleaning may help if the sensor is contaminated with oil or debris, but if the sensor is electrically faulty or the wiring is damaged, cleaning will not resolve the issue.