This week’s Diagnostic dilemma in the workshop Mercedes C220 Boost fault

We were asked to take a look at a Mercedes C220 that had a history of turbo boost faults . Initial questioning of the customer revealed it had already had new sequential turbos fitted but it would go into a default operating mode when held under load for a period of time causing a low boost fault code .

diagnostic testing , fault codes , rolling road
Mercedes C220 With a boost fault

 

Initial assessment confirmed the code and we could reproduce the fault as described on road test . An inspection of components revealed that the air filter was in a poor condition and the air intake pipe to the air mass meter had been damaged with these replaced and after carry out an inlet smoke test we retested the vehicle under sustained load on our rolling road but unfortunately the fault was still present even though all the acquired data showed correct parameters .

After seeking approval to proceed further we decided to confirm some of the data we had acquired  using a manual approach measuring turbo boost , DPF pressure and exhaust back pressure using  manual gauges . It was immediately obvious that the DPF pressure didn’t match the live data we were seeing via the scan tool and also there was excessive exhaust back pressure .

Dropping the exhaust after the DPF immediately revealed the issue the DPF has been removed and the rear of the exhaust was blocked with crystalised ad blue

Diagnostic , remapping , DPF
Blocked exhaust
Diagnostics, DPF Doctor
Missing DPF

 

The engine management system had been manipulated to take into account the DPF removal and maybe other items consequently the live data was of no use when trying to diagnose this issue .

We are seeing a growing amount of this type of fault software manipulation and poor remaps making the diagnostic process very difficult and time consuming , luckily we have the necessary equipment and knowledge along with our in house rolling road to go further than most specialists when it comes to diagnosing these types of issue’s .