With P248F the bank 2 bypass circuit is electrically sound, yet the flap does not do what the controller asks: it lags behind the setpoint, stops short of its end position or switching shows no effect on the gas temperature after the cooler. No manufacturer publishes a bank 2 version of this check. On bank 1 (P245B) GM's 2017 Duramax logic compares commanded and measured flap position and fails above a 16 % deviation, while Ford's 2023 diesels move the flap on purpose and expect a clear temperature response. A second bank would be judged the same way. Sticking from soot and oil carbon, a tired return spring, weak vacuum on pneumatic versions or wrong position feedback are the usual reasons. If the flap is later found fixed in place, the stuck code P24A6 may follow.
Medium severity. Can I keep driving?You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.
Bank 2 is the side without cylinder 1, so it only exists on V or boxer engines.
Symptoms
- Check engine light on
- Often no noticeable change in driving
Most likely causes
- Bypass flap on bank 2 sluggish from soot and carbon
- Leaking vacuum line or weak vacuum on pneumatic actuators
- Bank 2 position feedback reading off
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P248F means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 4: Emissions
- 8F: Specific fault in that system
Frequently asked questions
Can I keep driving with code P248F?
You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.
What causes code P248F?
The most common causes are: bypass flap on bank 2 sluggish from soot and carbon; leaking vacuum line or weak vacuum on pneumatic actuators; bank 2 position feedback reading off.
Related codes
- P245BEGR Cooler Bypass Control Circuit Range/Performance (Bank 1)
- P248EEGR Cooler Bypass Control Circuit/Open (Bank 2)
- P2498EGR Cooler Bypass Position Sensor Range/Performance (Bank 2)
- P24A6EGR Cooler Bypass Control Stuck/Open (Bank 2)
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.