OBD-II · Engine and powertrain (P)
P2BAC
NOx exceedance - EGR deactivated
What it means
NOx emissions may exceed limits because EGR has been switched off, either by a fault or by tampering. On vehicles with SCR, a confirmed unresolved fault may trigger reduced performance or a no-restart countdown; follow the displayed warning and the vehicle handbook.
Symptoms
- emissions warning; an AdBlue no-start countdown may appear on SCR-equipped vehicles
- engine warning light
- if a no-start countdown is displayed, restarting is inhibited when it reaches zero
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | EGR disabled by the ECU because of another stored engine or emissions fault |
| 02 | EGR electrical or mechanical fault |
| 03 | non-standard software disabling EGR |
What to check, step by step
- 01Read all engine and emissions codes and freeze-frame data; diagnose the primary fault that caused EGR to be disabled.
- 02Check EGR commands, position or flow feedback and the associated air-mass data using the OEM procedure.
- 03Test the EGR circuit or valve only when indicated by those results; check calibration if tampering is suspected.
- 04Repair the confirmed cause, restore approved calibration where necessary, and verify normal EGR operation.