P28F8 code meaning
Exhaust Pressure Too High Bank 2
Powertrain system Generic code P28xx codes Check engine light
What P28F8 means
P28F8 is the bank 2 twin of P28F7 and only appears on engines whose two cylinder banks have separately measured exhaust paths, such as V engines with one turbocharger or flap per bank. It means the exhaust pressure on that side exceeds the modelled value. No manufacturer documents P28F8 publicly; GM's 2025 diesel tables cover only the bank 1 code on an inline engine, where a stuck exhaust throttle plate caused a reading above 80 kPa under load. By analogy, a bank 2 fault would come from a flap, turbine or pipe restricted on the second side. DieselNet explains that higher back pressure raises fuel use and emissions and hurts performance. CARB requires monitoring of boost and aftertreatment systems for such faults. Comparing both banks helps: if only bank 2 is high, look downstream on that side.
P28F8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P28F8
- Check engine light on
- Loss of power, possibly with uneven running between banks
- Increased fuel consumption
Common causes of P28F8
- Most likelyExhaust flap or throttle on bank 2 stuck closed
- PossibleRestriction downstream on bank 2, for example a blocked catalyst or filter section
- Less likelyVariable turbine of the bank 2 turbocharger stuck in a closed position
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Exhaust pressure control valve bExhaust pressure sensor b2Particulate filterExhaust system
What each part of P28F8 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 8 | Area: transmission. |
| F8 | The exact fault in that area. |
What to do next
- Note P28F8 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P28F8
What does P28F8 mean?
P28F8 means "Exhaust Pressure Too High Bank 2". P28F8 is the bank 2 twin of P28F7 and only appears on engines whose two cylinder banks have separately measured exhaust paths, such as V engines with one turbocharger or flap per bank. It is a generic code, so it means the same on every make.
Is it safe to drive with P28F8?
Drive gently and only to a workshop. With P28F8 the car can go into limp mode (reduced power) to protect itself.
Will P28F8 fail an emissions test?
Yes, it can. P28F8 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P28F8 to fix?
Difficulty: medium. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P28F8 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.