P0405 code meaning
EGR Sensor A Circuit Low
Powertrain system Generic code P04xx codes Check engine light
What P0405 means
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. 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.
P0405 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyEasy, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0405
- Check engine light on
- EGR switched off
- Diesel: possibly reduced power
- Otherwise hardly noticeable
Common causes of P0405
- Most likelyWire or connector to the EGR valve open or shorted to ground
- PossiblePosition sensor in the EGR valve faulty (usually one unit with the valve)
- PossibleOlder Ford: DPFE sensor faulty
- Less likelyShared 5 V reference shorted
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR valve position sensorEGR valveSensor wiringEngine control module
What each part of P0405 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 05 | The exact fault in that area. |
What to do next
- Note P0405 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0405
What does P0405 mean?
P0405 means "EGR Sensor A Circuit Low". Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. It is a generic code, so it means the same on every make.
Is it safe to drive with P0405?
Drive gently and only to a workshop. With P0405 the car can go into limp mode (reduced power) to protect itself.
Will P0405 fail an emissions test?
Yes, it can. P0405 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0405 to fix?
Difficulty: easy. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0405 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.