Clear all DTCs to get us back to a clean page. After doing this, and performing a,data refresh the screen showed green ticks for every installed component (the yellow question marks indicate that an optional module is not fitted – for example don't have the TPM – Tyre Pressure Module).
Then disconnected the SDD and used the car as normal for a few days (putting up with the bongs/amber light occasionally) so that we had only the DTCs relating to the current state of the vehicle. After a few days I reconnected the SDD and started a new session with the vehicle before entering a “Diagnostics” session to perform a data collection. At this point we can see what DTCs have occurred since the clearing a few days earlier.
We can already see that there is one or more DTCs logged against the RLM (Ride Level Module) which we are interested in as well as one or more DTCs against the PCM (Powertrain Control Module) and TMC (Traffic Message Control Module). As the software’s name “Symptom Driven Diagnostics” implies it reads the information from the vehicle’s ECUs, you tell it what the symptoms are, it analyses the DTCs and tells you the most likely candidate for the fault.
For my suspension fault, I selected “Chassis > Suspension system > Vehicle dynamic suspension” and let the software work out what was happening. When the analysis is complete, you can view the DTCs found automatically grouped into events based on the symptoms you have specified.
In our case we have a single DTC linked in ‘Event 1’ and that it has a relevancy of 100% so this is probably the DTC for the suspension fault also the bulb icon indicates that this DTC caused a warning light to be lit (the amber suspension light) and the chain-link is unbroken which indicates that it is a current DTC rather than historical.
The other two DTCs under ‘unkown events’ are for a fault with one of the EGR valve sensors, which is probably means the valve is on its way out and should be replaced in the near future, and a loss of signal for TMC which I happen to know is due to bad coverage in my driveway but it works fine when out and about – these we can investigate later at our leisure.
Clicking on the RLM C1A20-64 DTC information ‘i’ icon brings up the help for this DTC.
Checking the ‘Symptoms’ matches exactly what is happening in this case perfectly. So we can look at the ‘Possible causes’ to narrow our search. Working backwards, we know the pressure sensor is working perfectly as it is detecting a loss of pressure (trying to raise the car can take much longer than expected and sometime doesn’t reach full height). None of the corner valves are stuck as this would be evident from dropping in the corner over night. The pipework and reservoir are all OK without any apparent leaks that are audible and the components all look sound. So it is most likely that the compressor is faulty or the filters/pipes are blocked or restricted.
