Used Control Unit Replacement and Brand Knowledge = Money Saving

This customers Mini came to us with a few strange faults after being parked up for a while over the lockdown. Both front windows not working, electric steering lock not working and various lights on the dash.

After plugging the vehicle into our Mini diag computer it was clear to see bizarrely we had separate faults for each item. Faults stored for both front window relays, so we thought we’d start here first to check/ fix the windows. After following steps, it located us to an internal fault with the relays within the FRM control unit. This unit controls the windows, lights and mirror functions. We removed to unit, removed outer cover to find a bit of moisture/ corrosion on the circuit board (suspect where it has been stood for a while). Carefully cleaned the board and refitted, hey-presto the front windows are now operational again. Sorted the first problem.

On to the electric steering lock not operating. When removing the key it should lock the steering, a clicking noise can be heard when operating, but nothing at the moment. Faults were stored for the CAS – steering lock road speed signal. Again following steps and with previous experience of this fault we saved a heap of time (and money). A known fault is a corroded wire under the battery tray between the CAS unit which is the vehicle immobiliser to the DSC/ ABS unit. The importance of this wire is providing a road speed signal to the CAS and steering lock. You don’t want the steering lock coming on whilst you’re driving along really!!

So we stripped the loom to find the corroded wire as suspected, repaired the damaged section. Refitted all parts and tested. Electric steering lock is now working again, great

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However we still had warning lights on the dash and a CAS control unit – internal fault remaining, that would not clear. We suspect the corroded wires have short circuited the CAS unit. Only option is to replace the unit, unfortunately a new one from BMW/ Mini is £350, ouch! These units are special order from Germany only as they are made specific to each vehicle as it has the relevant immobiliser/ security information inside them from BMW/ Mini.

However we have various specialist tools and software at our disposal here. So we were able to purchase a used CAS unit for £15 (that’s more like it). Wipe the stored info off the purchased used unit, transfer the info from the old unit on our purchased used unit.
Fitted the used CAS unit on to the car. Cleared all the faults. No warning lights now present and car is returned working correctly

It must also be said the customer of this vehicle was extremely patient and grateful of us repairing the vehicle this way. Always nice to be appreciated. We are looking forward to seeing it again for regular MOTs and servicing

If you want your BMW & Mini repairing correctly at the fraction of the cost of the dealership. Give us a call on 01425 277800
(Sorry for the poor quality photos, we’re better at fixing cars than pretty pictures)

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