P040C

EGR Temperature Sensor A Circuit Low

Q: Is it safe to drive with P040C?

Yes, in the short term — it's an emissions monitoring fault, not a driveability hazard. Repair it before an emissions test or long-term running.

Q: Can I just clear P040C?

It will return once the ECM re-tests the circuit. The sensor or its wiring needs to be repaired first.

Emissions (EGR) Generic OBD-II Medium

What it means

P040C means the ECM sees a lower-than-expected voltage from the "A" exhaust gas recirculation (EGR) temperature sensor. That sensor confirms hot exhaust is actually flowing through the EGR system; when its circuit reads low, the computer flags an emissions monitoring fault. It usually doesn't change how the car drives, but it is a sensor-circuit problem that needs the sensor or wiring repaired.

Medium

Can I keep driving? Safe to drive short-term — it's an emissions monitoring fault; you may notice little change, but the car can fail an emissions test.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

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
Often no noticeable change in how the car drives
Failed emissions test
Occasional rough EGR operation or slight loss of economy

Common causes

Most likely first

Failed EGR temperature sensor ALikely
Signal wire shorted to ground or open in the sensor circuitCommon
Loose or corroded connector at the sensorCommon
Carbon build-up on the sensor affecting its readingLess often
ECM fault (rare — verify the sensor and wiring first)Less often

How to diagnose & fix

Work through it in order

Scan and read freeze-frame data to confirm the fault is the EGR temperature sensor A circuit (not EGR flow).
Inspect the sensor connector and wiring for a short to ground, chafing, or corrosion.
Back-probe the sensor and compare its resistance/voltage to the temperature specification.
Remove and check the sensor tip for heavy carbon fouling.
Replace the EGR temperature sensor if it reads out of range with good wiring. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P040C?+

Yes, in the short term — it's an emissions monitoring fault, not a driveability hazard. Repair it before an emissions test or long-term running.

Can I just clear P040C?+

It will return once the ECM re-tests the circuit. The sensor or its wiring needs to be repaired first.

Read & clear P040C yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX