Error code

OBD2 P0129

OBD2P0129
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Barometric Pressure Too Low.

Severity

moderateCan be driven, but performance issues may occur.

Summary

P0129 indicates that the barometric pressure sensor is reporting an abnormally low reading to the powertrain control module (PCM). This can affect fuel delivery and ignition timing.

Symptoms

  • Hesitation upon acceleration
  • Diminished fuel efficiency
  • General lack of engine performance
  • Black smoke from exhaust
  • Excessively rich fuel delivery conditions

Common Causes

  • Defective MAP sensor
  • Faulty barometric pressure sensor (BPS)
  • Open or shorted wiring for the MAP sensor and/or BPS
  • Corroded connector face at the MAF/BPS sensor
  • Insufficient system ground at the MAF/BPS
  • Defective PCM or PCM programming error

Diagnosis

  1. Check for damaged wiring and corroded connectors.
  2. Perform an engine vacuum test to ensure proper operation.
  3. Inspect battery voltage capacity and alternator output.
  4. Test the MAP/BPS sensor resistance with a DVOM.
  5. Verify system reference voltage and ground signals.

Fixes

  • Replace faulty barometric pressure sensor or MAP sensor if necessary.

FAQ

What does P0129 mean?

P0129 indicates that the barometric pressure sensor is reporting an abnormally low reading to the PCM, which can affect fuel delivery and ignition timing.

How do I diagnose P0129?

Diagnose by checking wiring, connectors, vacuum levels, battery voltage, and testing the MAP/BPS sensor resistance with a DVOM.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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