P040AEGR Temperature Sensor A Circuit
- 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. P040A is its general circuit code. No manufacturer document available to us uses it – GM and Ford report this sensor as P040B to P040E – so the description follows CARB's requirement to check input circuits for continuity and range. A substitute value is used and the EGR cooler check is suspended.
- What you may notice
- Check engine light on
- Usually no change in driving
- Substitute value used, EGR cooler check suspended
- Likely causes
- LikelyConnector or wire at the sensor (heat, corrosion)
- PossibleSensor faulty
- RareEngine module input
- 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.