P040EEGR Temperature Sensor A Circuit Intermittent/Erratic
- 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. P040E means the signal jumps. GM diesels of 2016–18 set it when the measured resistance changes by more than 25 Ω between two samples 100 ms apart – faster than any real temperature change, so a loose contact or a cracked sensor is the cause (40 of 50 samples, MIL after two trips). Ford and GM's earlier Duramax LML do not use the code.
- What you may notice
- Check engine light on, may come and go
- No change in driving
- Likely causes
- LikelyLoose contact in the connector or chafed wire
- PossibleSensor with an internal hairline crack
- PossibleCorroded pins
- 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.