How to fix a P0402 fault code
P0402 can be an EGR valve stuck open, a sensor misreading or a control fault, and the fix is different for each. A £100 + VAT diagnostic at your home or workplace shows which one you'd be paying for.
Fix options for P0402 compared
| Fix | When it's the answer | Where it's done | Price |
|---|---|---|---|
| Mobile diagnostics | First, to see if the valve is really open too far or a sensor is wrong | Your home or workplace | £100 + VAT |
| New EGR valve | The valve is stuck open with carbon or its motor has failed | Garage | Garage quote |
| Sensor, solenoid or vacuum pipe repair | Live data shows a control or sensor fault instead of a stuck valve | Garage | Garage quote |
| EGR delete (software) | You'd rather switch the EGR off in the ECU than replace parts | Your home or workplace | £220 + VAT |
What P0402 means
The official wording is EGR flow excessive detected. The ECU has measured more exhaust gas returning to the intake than it asked for, usually by comparing the air flow sensor reading with what it expected for the valve position.
What causes P0402
- Carbon holding the EGR valve partly open
- A failed EGR valve motor or position sensor
- A sticking vacuum solenoid on vacuum-operated valves
- A faulty air flow sensor making the ECU think extra exhaust is coming through
- Wiring or connector faults on the valve circuit
Symptoms you may notice
Too much exhaust gas at the wrong time smothers combustion, so a rough idle, stalling when you pull up or hesitation from low revs are typical. Black smoke can appear as the air-fuel balance goes off.
Some vehicles feel fine apart from the engine light, especially if the valve only sticks now and then. If your Ford Ranger is showing P0402 with a lumpy idle, a valve held open by carbon is one of the first things to check.
Using the vehicle with P0402
You can usually carry on for short journeys, but stalling as you pull up in traffic is a safety risk, and extra soot heads into the DPF. The lit engine light fails an MOT, so get it diagnosed rather than living with it.
What happens on a P0402 visit
Fix the price up front
Diagnostics is £100 + VAT, done where the vehicle is parked.
Live EGR data
We command the valve and compare its position and the air flow with what the ECU expects.
Your result
You'll know whether it's the valve, a sensor or the control side. A garage fits any new part, with our findings to work from.
The delete option
An EGR delete is £220 + VAT and done on site. Rangers with the locked SID212 ECU are the exception, as that ECU is unlocked off site in 7 days for £1,200 + VAT. See our SID212 EGR delete page.
How much does it cost to fix P0402?
A wiring or vacuum pipe repair sits at the low end, and a new valve costs more. Our EGR valve replacement cost guide covers the valve, and the diagnostic tells you which you need.
Is it worth fixing P0402 on an older or high-mileage vehicle?
Usually, because a valve stuck open causes stalling and extra soot that can block the DPF. Compare the garage's quote with the vehicle's value once you know the cause.
Will replacing the EGR valve always clear P0402?
No. If the air flow sensor or a vacuum solenoid is at fault, a new valve won't change the reading. Testing first avoids buying a valve you didn't need.
Can you sort P0402 at my home or workplace?
We diagnose it on site, and the EGR delete is done there too. Replacement parts go through a garage.
Do I need a diagnostic before you can quote for P0402?
Can the vehicle go back on the road after an EGR delete for P0402?
No. An EGR delete is for off-road and export vehicles only, and our guide on whether an EGR delete is legal explains why.
Book the right fix for P0402
Tell us the registration and when the car stalls or runs rough, and we'll confirm the price before booking you in.
More fault codes explained
Eccles, Manchester M30 0SF