Mercedes E350 Heavy smoker under load

In the workshop this week a Mercedes E350 2012 CRD


Mercedes diagnostics

We were asked to help diagnose a very Smokey Mercedes E350 that seemed to be a problem that several garages had struggled to get to the bottom of.

After a discussion with the owner we ascertained that the vehicle had always had this issue since purchased just under a year ago, the symptoms were that the car would smoke heavily when driven under load above 3,000 rpm under all other driving conditions it was fine.

After a road test we could confirm that the fault was as described by the customer. Our initial diagnoses revealed no faults in the engine management system but there were some anomalies with some of the live data that caused us cause for concern this was noted and we carried on to complete our normal assessment routine including a pressurised inlet smoke test and a visual inspection of components and condition of service items .

The results of our assessment showed a well serviced vehicle with no obvious reason for the excessive smoke apart from the anomalies in the live data which related to the DPF live data it seemed that the engine management software may not be standard especially in relation the the DPF operation.

After consulting the owner, we took a read of the engine management software and had It analysed. We were not surprised to get a report back that the car had been remapped and not very well and also had a DPF delete in the software this was a surprise as the vehicle seemed to have a DPF fitted and it didn’t appear to have been tampered with. After further discussion with the owner we removed and inspected the DPF and found that the original DPF was still fitted but had suffered damage and the internal brick had broken up.







It was decided after further discussion to fit a new genuine DPF and return the engine management software back to standard. After completing the work, the vehicle was retested and the smoking had completely gone.


Obviously, the owner was unaware of the previous work carried out but we are seeing many cases of poor mapping causing running issues and vehicles that have had fault codes written out in the software to mask underlying faults which is making diagnosing faults much more difficult where this has been carried out.