P249B code meaning
EGR Cooler Bypass Position Sensor Circuit Intermittent/Erratic (Bank 2)
Powertrain system Generic code P24xx codes Check engine light
What P249B means
P249B flags short dropouts or implausible jumps in the bank 2 bypass position signal that are too brief to count as a steady low or high fault. Public manufacturer documentation for it does not exist, and even the well documented bank 1 sensor on GM's Duramax only has low, high and learning checks, without an erratic test of its own. If a controller does use P249B, the cause is rarely the sensor itself: heat cycling near the turbocharger, vibration and road splash attack terminals and harness on the second bank. A freeze-frame or a recorded drive helps to see under which load and temperature the signal breaks up. Fixing a terminal is usually enough; a new valve only follows if the fault lies inside. The bank 1 code is P2496.
P249B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P249B
- Check engine light appears now and then
- Bank 2 position value flickers in the live data
Common causes of P249B
- Most likelyFretting or loose terminal in the bank 2 sensor plug
- PossibleHarness brittle from heat near the turbocharger
- Less likelyIntermittent fault inside the sensor
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR cooler bypass position sensor b2
What each part of P249B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 9B | The exact fault in that area. |
What to do next
- Note P249B 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 P249B
What does P249B mean?
P249B means "EGR Cooler Bypass Position Sensor Circuit Intermittent/Erratic (Bank 2)". P249B flags short dropouts or implausible jumps in the bank 2 bypass position signal that are too brief to count as a steady low or high fault. It is a generic code, so it means the same on every make.
Is it safe to drive with P249B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P249B fail an emissions test?
Yes, it can. P249B 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 P249B to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P249B clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.