Renault Master RWD 0400F5 High Pressure Exhaust Gas Recirculation

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Renault Master EGR and DPF Cleaning: Resolving Common Faults

Emissions Faults on the Renault Master

When the vehicle was brought in, several warning lights were on, including the engine management light and a spanner light. The main error displayed was an anti-pollution system error, which is common with emissions-related issues. Running a scan revealed the following fault code:

P0400F5: High-pressure exhaust recirculation negative loop difference.

This pointed directly to a problem with the high-pressure EGR valve. Renault Master vans typically have both a high and low-pressure EGR system, meaning there are two EGR circuits responsible for recirculating exhaust gases. When the high-pressure system fails, it can easily trigger engine management errors.


Removing and Inspecting the EGR Valve

To understand the issue with this Renault Master, the first action was to remove the EGR valve and its associated components. The bolts on the EGR return pipe were loosened to give access to the valve itself. Right away, it was clear there was an issue. The EGR ports were almost entirely blocked with soot, which restricts the flow of exhaust gases back into the engine.

Interestingly, when the mechanic inspected the valve, it looked fairly new. On asking the owner, it turned out the EGR had been replaced less than a year ago by Renault. Despite this, the same issue had returned, indicating something more than just a faulty part – perhaps the van's driving habits were contributing to the recurring fault.


Cleaning the EGR and Ports

The clogged passages were treated with DPF cleaner to melt away the hard soot deposits. While chemical cleaning can remove a lot of the build-up, some of the tougher sections required manual scraping with a screwdriver.

After a thorough clean, the difference was remarkable. The amount of soot pulled out made it clear why the vehicle had lost EGR function.

Once cleaned, the EGR valve was refitted back to the intake manifold, and the electrical connections were restored. Any remaining fault codes on the system were cleared, and the van was ready for further checks.


The Accelerator Pedal Fault

Another code that appeared during this process was a fault with the accelerator pedal. This code can appear on these vehicles if the driver rests their foot on both the brake and accelerator at the same time. It's important to be mindful when operating the pedals, as putting too much pressure in the wrong position can confuse the system sensors. In this case, the fault wasn’t due to a mechanical issue with the pedal, more of an accidental input.


Checking the DPF Pressure Sensor

With the EGR problem resolved, the next issue to investigate was the DPF pressure sensor. The customer mentioned there had been DPF-related faults in the past, although these had been cleared before the van arrived for repairs.

Using live data while driving the van, the diagnostic charts were monitored to ensure the DPF wasn’t blocked. The pattern of the data showed the pressure sensor was reading correctly, but there was a moderate build-up of soot in the filter – approximately 16g.

For context, a healthy DPF should ideally be kept well below 6g of soot loading. To prevent future blockages, a DPF cleaning process was initiated to bring the soot level back down to a safer level.


The Big Picture

After resetting the vehicle and road testing it, everything was looking good. The fault codes stayed clear, and the DPF was functioning properly after being cleaned. However, the situation was still concerning – this particular EGR valve had been replaced just a year before. Renault had declined to replace it under warranty, citing the customer’s driving style as the cause of the issue.

For a 2020 vehicle with 54,000 miles on the clock, needing an annual clean or replacement of the EGR system isn’t a great sign. While clearing out the soot fixed the problem in this instance, without addressing the root of the issue (driving style or other underlying factors), it may become a recurring problem again in the future.


Conclusion

The Renault Master is a solid commercial vehicle, but like many diesels, it can be prone to EGR and DPF issues if not driven and maintained properly. In this case, a combination of driving habits and build-up of emissions-related deposits nearly sidelined the vehicle. After performing a thorough clean of the EGR and DPF systems, the van was given a new lease of life without needing any major replacements.

If you've had recurring issues with your EGR valve or have seen the anti-pollution error on your dash, it's worth checking the EGR and DPF for blockages before jumping to any expensive conclusions. Keeping an eye on your driving style and staying on top of these emissions-related components can prevent you from dealing with more serious repairs down the road.