06/11/2025
This BMW X3 cut out on its owner, and became a crank no start. It was recovered back to their local garage, where it restarted with no issue.
After scanning the car for fault codes and seeing that the crank sensor and exhaust backpressure sensor had codes stored, but both seemed to be working ok, they sent the car away.
3 days later it happened again, same story, cut out and wouldnt restart, recovered to the garage, same codes, and would start back up and run fine.
At this point it got a new crank sensor, and a new pressure sensor to 'rule them out'
Needless to say, it didn't fix it....
Unfortunately for our customer, this was a car theh had recently sold, so their client (understandably) was unhappy with their purchase and wished to return it if it couldnt be fixed.
They called us in straight away, using our process quickly found that there was a huge clue sat amoung the stored fault codes - Voltage supply 3 short to ground. A quick read up showed the voltage supply 3 referred to a 5vref circuit, and it feed the crank sensor and the back pressure sensor.
Upon testing these supplies, it was found that sure enough the voltage was being pulled down. Its not uncommon for a failed sensor to do this and effect the supply to all sensor fed from the same regulator, but in this case with all the voltage supply 3 sensors unplugged it was still short to ground.
Didn't take long to find out why, using a logical approach looking for contact points, missing clips, or incorrect routing of the loom..... Bingo! That loom should not be sat atop the exhaust like that!
Just look at the damage the heat had caused!
Not a huge repair, and access was pleasant. Now everyone is happy and the car is back on the road (oh, and the loom is back in its correct home!)