OBD-II fault code

P28F8: Exhaust Pressure Too High Bank 2

What it means

The exhaust pressure measured on bank 2 exceeds the calibrated maximum. Common causes are clogged DPF, restricted exhaust path, or stuck exhaust brake/back-pressure valve.

At a glance

  • Usually lights the check-engine light
  • Affects emissions; the car can fail an emissions test
  • The engine or gearbox may go into limp mode

How it works

The exhaust pressure sensor on bank 2 measures back pressure in that side's exhaust path so the engine control module can assess flow and emissions equipment operation. This code sets when bank 2 pressure exceeds the calibrated maximum, often because a DPF or other exhaust path is restricted or a back-pressure valve is stuck closed.

Common causes

Most likely first.

  1. DPF clogged with soot or ash
  2. Back-pressure valve stuck closed

Symptoms

  • Check-engine light
  • Reduced engine power
  • Poor acceleration

How to diagnose it

  1. Record freeze-frame data and check scan-tool exhaust pressure, soot-load, and regeneration data for bank 2 before clearing the code.
  2. Inspect the bank 2 exhaust path and pressure sensor hoses or ports for damage, blockage, leaks, or disconnected fittings.
  3. Check whether a back-pressure valve on the bank 2 path is stuck closed or fails to respond to commands, using the manufacturer's procedure.
  4. Assess the DPF restriction and soot or ash loading on bank 2 using scan data and the manufacturer's diagnostic procedure.
  5. If the exhaust path is clear, test the bank 2 pressure sensor and its wiring against the manufacturer's specification.

Common fixes

  • Clear a blocked bank 2 pressure sensor port or repair a damaged pressure hose.
  • Repair or free a stuck back-pressure valve on the bank 2 exhaust path.
  • Perform the manufacturer-approved DPF regeneration if soot loading allows it.
  • Clean or replace a DPF that is restricted beyond the manufacturer's service limits.

Can I keep driving?

Reduced power and poor acceleration indicate the bank 2 exhaust may be significantly restricted, and continued driving can worsen heat and engine stress. Avoid towing or hard acceleration, and stop if power drops sharply or warning messages require it.

A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together

This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.

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