P28F7Exhaust Pressure Too High Bank 1
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P28F7 reports that the pressure in the exhaust of bank 1 is higher than the engine model allows. GM documents it in its 2025 diesel ECM tables (25OBDG04B): the monitor looks at the low-pressure EGR differential pressure and fails above 80 kPa while torque demand exceeds a speed-dependent minimum (around 520 Nm at low engine speed, falling to 20 Nm at high speed), counting 480 failures in 600 samples; it is Type A, MIL on the first trip. GM names the cause as an exhaust throttle valve in the wrong position, for example with the link between its upper and lower shafts broken so the plate can stay shut although the actuated shaft has moved. GM bulletin 21-NA-149 lists P28F7 for the 3.0 L LM2 Duramax. Excess back pressure costs power and fuel and stresses the turbocharger.
- What you may notice
- Check engine light on
- Reduced engine power
- Higher fuel consumption and more frequent filter regenerations
- Likely causes
- LikelyExhaust throttle valve stuck closed or its shaft linkage broken
- PossibleExhaust restricted downstream, for example by a heavily loaded particulate filter or damaged pipe
- RareChafed engine harness disturbing valve control (GM 21-NA-149)
- RarePressure sensor reading too high without a separate sensor code
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €150 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.