How to fix a P0405 fault code
P0405 is often a wiring fault rather than a failed valve, so the cheapest fix can be a repair to the loom. A £100 + VAT diagnostic at your home or workplace shows which part needs paying for.
Fix options for P0405 compared
| Fix | When it's the answer | Where it's done | Price |
|---|---|---|---|
| Mobile diagnostics | First, to test the sensor signal, supply and earth | Your home or workplace | £100 + VAT |
| Wiring or connector repair | A short to earth or a damaged pin is pulling the signal low | Garage | Garage quote |
| New EGR valve (sensor built in) | The sensor inside the valve has failed | Garage | Garage quote |
| EGR delete (software) | You'd rather switch the EGR off than keep repairing it | On site | £220 + VAT |
What P0405 means
The official wording is EGR sensor A circuit low. The sensor reports the EGR valve's position to the ECU, and its signal voltage has dropped below the lowest figure a working sensor should produce.
What causes P0405
- A chafed wire shorting the signal to earth
- A corroded or loose connector at the EGR valve
- A failed position sensor, which on most engines is built into the valve
- A fault on the sensor's 5-volt supply, sometimes shared with other sensors
Symptoms you may notice
Many vehicles show nothing beyond the engine light, as the ECU may simply stop using the EGR valve. Others idle roughly or lose a little power. If other sensor codes appear at the same time, a shared supply fault is likely.
Using the vehicle with P0405
Most vehicles run normally enough to keep using for now, but the EGR system isn't being controlled properly and the lit light fails an MOT. If your Ford Ranger is showing P0405 with limp mode, get it checked sooner.
What happens on a P0405 visit
Price agreed first
Diagnostics costs £100 + VAT and happens where the vehicle is parked.
Circuit testing
We check the sensor's supply, earth and signal, and watch the reading as the valve is commanded to move.
The result
You'll know whether it's wiring, a connector or the valve. Wiring and valve repairs go to a garage with our findings.
The delete option
An EGR delete is £220 + VAT and done on site. Rangers on the locked SID212 ECU need it removed and unlocked off site, which is £1,200 + VAT with a 7-day turnaround.
How much does it cost to fix P0405?
A wiring repair is usually cheaper than a valve. Our EGR valve replacement cost guide covers the dearer end, and the diagnostic tells you which you need.
Is it worth fixing P0405 on an older or high-mileage vehicle?
Yes, if it's staying on the road, as the warning light alone fails the MOT. Wiring faults are often a small job.
Will replacing the EGR valve always clear P0405?
No. A new valve won't help if the wire to it is shorted or the supply has failed. Test the circuit before buying.
Can you sort P0405 at my home or workplace?
We diagnose it there and can carry out the delete on site. Wiring and valve repairs go through a garage.
Do I need a diagnostic before you can quote for P0405?
Yes. Without testing the circuit nobody can say whether it's a wire or the valve. Its opposite code is P0406, for a signal reading high.
Can a vehicle with an EGR delete for P0405 go back on the road?
No. The EGR delete is for off-road and export vehicles only, and our guide Is EGR delete legal? explains why.
Book the right fix for P0405
Send us the registration and any other codes on the reader, and we'll confirm the price and a time before booking.
More fault codes explained
Eccles, Manchester M30 0SF