I'd be interested in knowing what code has us replace any part without some sort of testing to verify that it is the part at fault. Too many times, I see a DIYer replace hundreds of dollars worth of parts needlessly.... sometimes leaving a chain of problems in his wake. Spread connector pins and pierced insulation can be the hardest to find - especially when someone has been probing wires with no rhyme or reason.
I'm all for a DIYer saving himself some money, but we need to have some sense when we're working on these things....
Had one in the shop last week... F150 for a no start after a stereo and subwoofer install..... It wasn't hard to find the body wiring harness (the,uhhhh, $1600 body wiring harness ) that got drilled through. After the wiring repairs, it still wouldn't start and displayed some of the oddest symptoms we have ever seen. KOEO, the vapour management valve (purge valve to some) would "pulse" rapidly and the theft light would blink in time. Unplug the VMV and the electronic throttle control motor would start pulsing... again, joined by a synchronized blinking of the theft light.
A day and a half later, we found the cut wire in the left door sill bundle.... "Oh, yeah.... I guess I should have mentioned that....". Lessee.... 12 hours at 95 bucks plus GST....