P0405

EGR Sensor A Circuit Low

Emissions / EGR Generic OBD-II Medium

What it means

P0405 means the EGR position sensor "A" signal is reading below its valid range — typically a short to ground or an open in the circuit. That sensor tells the ECM how far the EGR valve is open, so with a faulted signal the ECM can't verify EGR flow. The car usually still drives, but EGR problems can cause a rough idle and will fail emissions. The cause is generally the wiring or the sensor itself.

Medium

Can I keep driving? Yes — the car generally drives fine, though EGR faults can cause a rough idle or light hesitation; it will fail an emissions test until fixed.

Real-world scan data

Seen in

2,393

scans in the past year

Found in

0.4%

of scans

0.7%

of scans that found faults

Appears alongside · share of P0405 scans

P0403in 19.6% of scans

P0401in 16.3% of scans

P0406in 14.5% of scans

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
Rough idle or light hesitation in some cases
Slightly reduced fuel economy
Fails an emissions test

Common causes

Most likely first

Signal wire shorted to ground or open in the EGR position-sensor circuit — most commonLikely
Failed EGR position sensorCommon
Corroded or loose connector at the EGR valve/sensorCommon
Poor sensor ground or reference-voltage faultLess often
Faulty ECM (rare)Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data and confirm the EGR position signal is reading low/near zero.
Inspect the EGR valve/sensor connector and wiring for damage, corrosion, or a short to ground.
Check the sensor's reference voltage and ground against spec.
Test the position sensor's output as the EGR valve moves; replace the sensor (or valve assembly) if it won't respond.
Clear the code and drive a cycle to confirm the repair.

FAQ

Quick answers

Is it safe to drive with P0405?+

Yes, short term. The engine runs, though you may notice a rougher idle. Fix it to restore proper EGR operation and pass emissions.

Can I just clear P0405?+

It returns once the circuit reads low again. The sensor or its wiring needs repair.

Read & clear P0405 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