P040D
EGR Temperature Sensor A Circuit High
EGR / emissions
Generic OBD-II
Medium
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.
Medium
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.
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?+
Yes — it's a sensor and emissions fault, not a driveability hazard, but it will likely fail an emissions test until fixed.
Can I just clear P040D?+
It returns once the ECM rechecks the circuit; repair the sensor or wiring first.
Related codes
Often seen with P040D
Read & clear P040D yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX