Hi everyone,
Ok, so I have an 2012 Cooper Coupe R58 with close to 200k mi on the chassis. I recently changed the brakes on all 4 corners and about a week later I am getting DSC failed warning on the display. When checked with a Foxwell scanner, I'm getting multiple (9) DSC codes including yaw sensor fault, longitudinal accelerator sensor fault, multiple DSC "no DSC message", and multiple (4) CAS codes as well, CAS Control Unit fault, CAS 1,2,3 terminal 15 outlet faults ... The car has refused to start a couple of times when start button is iniitally pushed but then will start if pushed again - The battery is new and coded to the car, the key fob is new and was coded by a dealer, the charging system is showing 12.3v cold and goes immediately to 14.3v after start, the ground cables are both intact and I have cleaned the contact points ensuring they are bare metal. The FRM was rebuilt and recoded about 6 mos ago. There was no water intrusion or corrosion in the footwell or floor at the time. Has anyone experienced all of these problems concurrently? ANY ideas of where to go from here will be appreciated. I gotta get this fixed, it's driving me nuts!

 

Did you knock or break one of the speed sensors during the service?

 

Will be double checking all 4 later today.

 

Would help if you post all of the fault codes.

 

Just drove and live tested the speed sensors - all are reading accurately and for a decent distance

 

 

That's a complex set of fault codes, all of which could potentially be caused by an intermittently failing CAS module.

However, before deciding on any direction to take, first clear all of the fault codes and then turn ON the ignition key without starting the engine to check which codes, if any, return. Post all codes that return after clearing the current ones.

 

Yes, have done this many times over the past few days ... same codes reappear .... I'm leaning towards a JBE module - lots of relay clicking noises coming from the passenger footwell area, random failure codes for taillights that are obviously not failed .. all of these codes are power related, etc

 

Just to clarify, are you saying that after clearing the codes, all the codes return after turning the ignition ON without starting the engine?

 

Yes, exactly

 

Actually, NO, strike that ... the codes reappear only after starting the engine after clearing them in the case of the CAS codes ... only after putting the car in motion for the DSC codes

 

Start here:
Clear all fault codes again, and then use your Foxwell scan tool to recalibrate the steering angle sensor. When done, drive the car to see whether the DSC fault codes do not return.

 

Checked steering angle sensor when this first started - it is correct

 

Did you do the recalibration procedure? And can you describe how you assessed the steering angle readings?

 

yes, recalibration was done - read via scanner with vehicle running on level ground, steering wheel straight, read 0deg

 

Use your scan tool to graph the CAS module voltages at both terminal 30 and terminal 15 before and after you start cranking the engine. Post your graphs.

 

Top to bottom = from fob inserted, crank, engine running
Today the car is also intermittently not starting on the first push of the button ... Starter flutters like low voltage, then the car will start after the 3rd or 4th push of the button - battery, again, is brand new and passes load test, yes, it was coded to the car

Thank you for all your input, btw, I have been remiss in saying that 🙏

 

Interesting.
However, you only mention three conditions above but show 4 images. Please list the four conditions matching the images.

Can I assume that the second image is the initial cranking?

 

Since I can't post a video, there is a few seconds in photo snaps ... 1 key fob inserted, 2 cranking, 3 continued cranking, 4 engine has started

 

JBE is now popping a code as well

 

#3, 5 &6 are saying the failure is due to no message from the CAS transmitter

I'm just about convinced that the CAS module has given up

 

Image #2 reveals the likely underlying issue causing all of the problems. During cranking, the terminal 30 and terminal 15 voltage should not drop below 9.6V. Your voltages drop as low as 8.6V, likely causing the CAS to stop processing (code A0A9), the DSC to reboot, and the JBE to stop receiving voltage from the CAS (code C91E).

Possible causes of the low voltage spike:
1) Excess resistance in the engine ground wire.
2) Excess resistance in a battery-connector to battery post connection.
3) Excess resistance in the battery cable to starter/alternator harness connection.

 

My interpretation of code C91E is that the excessive voltage drop during cranking prevents the CAS module from communicating with other modules on the CAN-bus.

Another possible cause of the cranking voltage drop is a faulty starter motor that draws excessive amperage.

A simple way to test for a bad engine ground wire is to connect one end of a battery jumper wire to the (-) battery terminal and the other end to a clean, unpainted bolt on the engine block. Then redo the Foxwell voltage drop test.

 

I did remove and clean the ground points on the engine and chassis, the strap itself does not look to be corroded but I'll replace it anyways. I may get the neg cable for the battery as well. I'll post back with the outcome.
Thank you so much for taking the time to help with this problem!

 

So, thanks to maybe, maybe not, I think this problem is solved! It was the starter - I went ahead and replaced it about a week ago, cleared codes and have had zero problems since ... Thank you soooo much, maybe, maybe not ... Lifesaver!