P0129
Barometric Pressure Too Low
Fuel & air metering
Generic OBD-II
High
What it means
P0129 means the barometric pressure the ECM reads (usually from the MAP/BARO sensor at key-on) is lower than it should be for the vehicle's altitude. The ECM uses barometric pressure to correct fueling and timing, so a low reading can cost a little power and economy. It's typically a sensor, wiring, or vacuum-leak issue rather than anything that stops the car.
High
Can I keep driving? Generally safe to drive — the engine may feel slightly down on power or use a bit more fuel, but a low barometric reading won't strand you.
Common symptoms
What you'll notice
- Check-engine light on
- Slight loss of power or hesitation
- Minor drop in fuel economy
- Rough running, more noticeable at high altitude
Common causes
Most likely first
- Faulty barometric/MAP pressure sensor (often the same sensor)Likely
- Vacuum leak affecting the pressure readingCommon
- Open, shorted, or corroded wiring at the sensorCommon
- Rarely, an ECM/PCM faultLess often
How to diagnose & fix
Work through it in order
- Compare the sensor's barometric reading at key-on against actual local pressure for your altitude.
- Inspect the sensor connector and wiring for damage or corrosion.
- Check for intake vacuum leaks that could skew the pressure reading.
- Replace the MAP/BARO sensor if it reads consistently low. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0129?+
Yes, generally. You may notice slightly reduced power or economy, but the engine remains driveable; still fix it so fueling stays accurate.
Can I just clear P0129?+
You can, but if the sensor or a vacuum leak is skewing the reading, the code returns after the next drive cycle.
Related codes
Often seen with P0129
Read & clear P0129 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX