P040BEGR Temperature Sensor A Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- EGR temperature sensor A measures the gas temperature in the EGR path – for cooler monitoring, component protection and the EGR model. Whether it sits before or after the cooler depends on the maker: GM diesels have sensor A after and B before the cooler, Ford diesels sensor B after it. Like a coolant sensor it is an NTC, so a low voltage means hot. P040B is its plausibility check: after a cold start the sensor must warm up once hot exhaust flows. Ford diesels set the code if it rises by less than 10 °C after load; GM diesels if it barely changes after at least 8 hours off and a defined EGR flow (MIL after two trips). A sooted sensor tip or a lack of EGR flow are typical causes.
- What you may notice
- Check engine light on
- Usually no change in driving
- Substitute value used, EGR cooler check suspended
- Likely causes
- LikelySensor sluggish, tip sooted
- PossibleSensor drifting or faulty
- PossibleNo EGR flow (valve or cooler blocked), sensor sees no heat
- RareContact resistance in the connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €50 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.