EGR Temperature Sensor A Circuit High
What it means
P040D means the EGR temperature sensor "A" circuit is reading abnormally high — typically an open circuit or a sensor signal above its normal range. This sensor tells the ECM how hot the recirculated exhaust gas is so it can confirm EGR flow. It's an electrical sensor-circuit fault; the engine keeps running, but EGR monitoring and emissions are affected.
Can I keep driving? Driveable — this is an emissions monitoring sensor, so the car runs normally; the main consequence is a warning light and a likely emissions-test failure.
Real-world scan data
Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.
Common symptoms
What you'll notice
- Check-engine light on
- Likely failed emissions test
- Little or no change in how the car drives
- Possible related EGR fault codes
Common causes
Most likely first
- Faulty EGR temperature sensor ALikely
- Open circuit or short to voltage in the sensor wiringCommon
- Loose or corroded sensor connectorCommon
- Sensor contaminated by heavy carbon buildupLess often
- Faulty ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and note the sensor's reported temperature.
- Inspect the sensor connector and wiring for opens or shorts to power.
- Measure the sensor's resistance and compare it against its temperature spec.
- Replace the EGR temperature sensor if it reads out of range.
- If wiring and sensor are good, evaluate the ECM. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P040D?+
Can I just clear P040D?+
Related codes
Read & clear P040D yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.