P28F9
Exhaust Pressure Too Low Bank 1
The exhaust pressure measured on bank 1 falls below the calibrated minimum. Common causes are leaks upstream of the sensor, missing DPF substrate, or sensor calibration drift.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Exhaust leak upstream of sensorCommon
- Sensor zero point driftedPossible
Parts involved
- Exhaust Pressure Sensor B1
- Particulate Filter
- Exhaust System
P28F9 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.