EGR position sensor signal high.
P0406 — also written PO4O6, P 0406, 0406 — is the OBD-II code for egr sensor 'a' high. Same code, same fix: this page covers every spelling of it.
P0406 usually means the ECU is seeing a voltage signal from the Exhaust Gas Recirculation (EGR) valve that's way higher than it expects—usually because the internal sensor has packed up or the wiring has rubbed through. It's a classic headache on the 2.7 CRD engines and older Vauxhall diesels.
P0406 is a emissions fault code, typically costing £100–£400 to put right in a UK garage.
What P0406 actually feels like to drive
- The car 'kangaroos' or hesitates when you're cruising at 30mph on a steady throttle.
- A sudden 'Limp Home' mode that clears if you cycle the ignition, only to return 5 miles later.
- Engine Management Light (EML) staring you in the face on the dashboard.
- Rough idling at the traffic lights, feeling like it wants to stall.
- A noticeable drop in MPG because the ECU is using 'default' fueling maps.
What causes P0406?
- Sensor failure
- Wiring short
UK vehicles that throw P0406 most often
- Chrysler 300C 3.0 V6 CRD (2005-2010)
- Vauxhall Astra J 1.7 CDTi (A17DTR engine)
- Ford Transit 2.4 TDCi (Puma engine) 2006-2011
- Land Rover Discovery 3 2.7 TDV6 (early models)
- Jeep Grand Cherokee 3.0 CRD (2005-2010)
- Vauxhall Corsa D 1.3 CDTi (Z13DTJ)
How P0406 is fixed
- Sensor replacement
The P0406 misdiagnosis that wastes money
I see folks panic and replace the entire EGR valve assembly or the ECU because they think 'sensor high' means the whole brain is fried. In my experience, especially on the Chrysler 300C or the older Vauxhalls, the valve itself is usually just fine but the internal potentiometer is toast. I've had lads spend £300 on a genuine valve when a bit of loom repair or a targeted sensor swap would've done it. Also, don't just spray EGR cleaner down its throat; that won't fix a high voltage circuit fault, it'll just make your driveway messy.
What a UK garage should charge for P0406
For a standard UK independent garage, you’re looking at £50 to £80 for a proper diagnostic plug-in. If it’s just the sensor or a simple valve swap, parts like a Delphi or Bosch unit usually run between £80 and £180. Add in 1-2 hours of labour at £60-£90 an hour, and you're typically out the door for £250. If you go to a main dealer like Stellantis or Ford, expect to pay north of £450 once they've added their 'premium' labour rates and 20% VAT on everything.
P0406 repair cost in the UK
Most P0406 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 P0406
Before you let a garage charge you for a new EGR, ask them to do a 'pin-out test' on the 5-volt reference line. If that sensor is seeing 5V when it should see 0.5V at idle, it’s often a short in the loom rubbing against the engine block. If you’re buying parts, avoid the unbranded eBay specials—they’re 'D.O.A.' half the time. Stick to Delphi, Wahler, or Pierburg. If your car is a diesel and the EML (Engine Management Light) is on for this, it’s an automatic MOT fail under the new rules, so don't leave it until the day before your test.
Can you drive with P0406?
Drivable.
Urgency: medium.