P040A
EGR Temperature Sensor A Circuit
EGR / emissions
Generic OBD-II
Medium
What it means
P040A means the engine computer detected a circuit fault in EGR temperature sensor A, which monitors the temperature of recirculated exhaust gas. This is a sensor-circuit code — not the EGR valve — so it usually has little effect on drivability but will keep the check-engine light on and can fail an emissions test. It most often traces to the sensor, its wiring, or carbon fouling.
Medium
Can I keep driving? Safe to drive; this is an emissions-monitor fault with little effect on how the car runs, though it may fail an emissions test.
Common symptoms
What you'll notice
- Check-engine light on
- Often no noticeable change in how the vehicle drives
- May fail an emissions/readiness test
- Possible slight drop in fuel economy on some vehicles
Common causes
Most likely first
- Faulty EGR temperature sensor ALikely
- Open, shorted, or corroded wiring in the sensor circuitCommon
- Loose or corroded connector at the sensorCommon
- Heavy carbon buildup around the sensor affecting its readingLess often
- Failed engine control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the code is the EGR temperature sensor A circuit (not the EGR valve itself).
- Inspect the sensor connector and wiring for damage or corrosion.
- Check the sensor's resistance/signal against temperature spec with a scan tool.
- Clean carbon from the sensor tip if fouled, or replace the sensor if it's out of spec. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P040A?+
Generally yes — it's an emissions sensor fault and rarely affects drivability. Get it fixed before an emissions test, though.
Can I just clear P040A?+
It will clear, but returns until the EGR temperature sensor or its wiring is repaired.
Related codes
Often seen with P040A
Read & clear P040A 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