EGR position sensor signal low.
P0405 — also written PO4O5, P 0405, 0405 — is the OBD-II code for egr sensor 'a' low. Same code, same fix: this page covers every spelling of it.
This code means the ECU can't hear what the EGR valve is doing because the voltage signal has dropped through the floor. It’s a classic headache on high-mileage UK diesels like the Ford Transit or Vauxhall Vivaro.
P0405 is a emissions fault code, typically costing £100–£400 to put right in a UK garage.
What P0405 actually feels like to drive
- The car 'kangaroos' or hesitates when you're cruising at 30mph on a light throttle.
- Total lack of power below 2,000 RPM, then suddenly kicks in like a mule.
- Dashboard displays 'Engine Service Now' or the amber 'helicopter' EML light.
- Rough idling at the traffic lights, sometimes feels like it's about to stall.
- A noticeable drop in MPG because the ECU is running on 'safe' default maps.
What causes P0405?
- Sensor failure
- Wiring open
UK vehicles that throw P0405 most often
- Ford Focus/Fiesta 1.6 TDCi (DV6 engine) 2008-2015
- Vauxhall Insignia 2.0 CDTi (A20DTH) 2009-2017
- Volkswagen Golf/Passat 1.6 & 2.0 TDi (EA189 engines) 2009-2015
- Land Rover Discovery 3/4 2.7 TDV6 (notorious for EGR failure)
- Citroen Berlingo/Peugeot Partner 1.6 HDi van variants
How P0405 is fixed
- Sensor replacement
The P0405 misdiagnosis that wastes money
I’ve seen too many lads just chuck a cheap eBay EGR valve at this because the code says 'Low Signal'. Usually, it’s not even the valve that’s dead; it’s the wiring loom chafing against the gearbox casing or the battery tray. On the 1.6 TDCi Fords especially, the pins in the connector get 'green rot' (corrosion). You can fit a brand-new Pierburg valve, but if that 5V reference wire is broken or shorted to ground, you’re just swapping a good part for a new one and the light will stay on. Check your feeds and grounds first.
What a UK garage should charge for P0405
For a standard 1.6 diesel, expect to pay £45-£70 for the initial diagnostic plug-in. A quality OEM EGR valve (like a Delphi) usually costs between £130 and £220. Labour is typically 1 to 2 hours (£60-£150 depending on local rates), bringing the total to about £250-£380. If you go to a main dealer, they’ll easily quote you £600+ because they’ll insist on using their branded boxed parts which are identical to the Bosch ones I use anyway.
P0405 repair cost in the UK
Most P0405 repairs land between £100–£400 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0405
If your garage tells you it's a 'blind' swap, ask them if they've checked the 5V reference circuit. A proper tech will spend 20 minutes with a multimeter before ordering parts. If the valve is confirmed dead, don't let them fit a 'white box' unbranded part to save £40—they’re rubbish and usually fail within three months, triggering the light again. Insist on OE brands like Bosch, Delphi, or Wahler. Also, ask if they’re going to perform the 'EGR adaptation' or 'relearn' with the diagnostic tool; if they don't, the ECU might not recognize the new sensor positions.
Can you drive with P0405?
Drivable.
Urgency: medium.