Ford transit particulate problems

So this week was the turn of a 72 plate transit. This time it was a particulate after sensor fault. Faulty unit! I hear you cry...that's what one of my colleagues thought when he fitted the replacement. But the fault stubbornly wouldn't go away. So the job comes to me. I test it and see I am getting CAN signals and some power. 5V to be exact. But wait, these are 12V sensors? What's going on? This stumped me. I'll admit. But not for long. I soon figured out that something was stealing power,but where? I turned to Halfords workshop. Initially, I was getting nowhere. Finally I found a fuse. Armed with this and a multimeter I could start testing. 

Power to the fuse - check 

Fuse not blown - check

Power on the wiring after the fuse...mostly. 

Following the wire through the harness was the tricky bit. Eventually I found exactly where it went. Which connectors it travelled through, and where I need to look. 

So after all this. The sensor and controller was good

The fuse was good.

The wiring in the engine bay was good. 

That just leaves the 5 metres that run under the chassis. No sweat, right? 

After carefully examination. I started splitting the cover off the harness. Less than a metre in and a ugly green lump appears in the wiring. Hey presto! We found it! After chopping back all the rotten copper. I spliced in a new section. Fingers crossed. I started the van up and checked for faults. All clear! Happy Days! 

I get the wiring all sealed up again and back to factory standard. Everything cleared up and car is ready to get back to the customer.