EngineLightCodes
Powertrain code

P0405 EGR Sensor A Circuit Low

Severity
Fix soon
Typical repair cost
$30–$660
Do it yourself
Possible, easy
Shop time
0.5–2.5 hours

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx.

How the engine computer detects it

EGR sensor A is usually the valve position sensor with a 5 V supply; on Ford until about 2011 it was the DPFE differential pressure sensor. P0405 means its signal is below the lower limit – GM 2018 below 11 % of 5 V (MIL after two trips), Ford below 5 % of full scale for 4 s, Saab below 0.26 V. The cause is a short to ground or an open signal or 5 V wire. EGR position control is then switched off.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

  • Check engine light on
  • EGR switched off
  • Diesel: possibly reduced power
  • Otherwise hardly noticeable

Common causes

  1. Wire or connector to the EGR valve open or shorted to ground Most likely
  2. Position sensor in the EGR valve faulty (usually one unit with the valve) Possible
  3. Older Ford: DPFE sensor faulty Possible
  4. Shared 5 V reference shorted Less likely

How to diagnose P0405

  1. Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
  2. Inspect the parts involved: egr valve position sensor, egr valve, sensor wiring, engine control module.
  3. Work through the causes above from most to least likely, cheapest checks first.
  4. Clear the code and drive a full drive cycle to confirm the repair held.

Vehicles that report P0405 most

VehicleYearsReportsMedian miles
Chevrolet Volt2016–20173—

Counts of owner complaints to the NHTSA that mention P0405 (11 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.

Reading the code

P
Powertrain
0
Generic (SAE) code
4
Auxiliary emission controls
05
Specific fault

Questions drivers ask

Can I drive with code P0405?

Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.

Will my car pass an emissions inspection with P0405?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Will P0405 clear by itself?

The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.

Can I fix P0405 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.

Often reported together

Codes that owners mention in the same NHTSA complaints as P0405. They can point to a shared cause, so it's worth checking them together.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.