Recently in the workshop a Mini cooper with no power steering , this vehicle had quite a history of repair and unsuccessful attempts to resolve this issue . The vehicle had already had two secondhand steering racks and on arrival was fitted with a reconditioned steering rack non of which had effected a cure . Initial investigation confirmed that the vehicle had no power steering assistance and the steering warning lamp was illuminated on the dash .
Vehicle scans confirmed that there was no communication with the power steering control unit although all other control units were working and communicating correctly.
Consulting manufacturers wiring diagrams we set about finding the route cause of this problem . The first step was to confirm that the power steering control unit had correct voltage supply and ground this was in place and was able to sustain a load so no fault there . We then turned our attention to the can bus communication network using our Pico scope we are able to test this in real time to see what was happening. Once displayed live on the scope it was obvious this is where the fault was a incorrect scope trace indicating can bus issues . Reporting back to the owner we were given approval to investigate further and we found a can bus wiring issue in the nearby loom . Once repaired the can bus trace was normal and communication was restored to the control unit along with correct power steering assistance .
If this vehicle had been checked using a logical approach with the correct information and equipment it may not have needed a new rack let alone three. Whilst correct diagnoses may seem expensive it so often works out cheaper in the long run with no wasted parts fitted .
