After fixing up my Envoy I have been having so many issues with the dreaded P0526 code for the cooling fan sensor circuit. The problem was intermittent and for the life of me I couldn't figure it out. I must have checked the wiring harness 10 times and was positive the wires were not damaged. The other day i decided to take another look. This time i took apart the actual plug and removed every wire from it. There was a spot on the black ground wire very close to the connector that felt flimsy. I connected my multimeter to the battery positive and the other end to the ground wire pin from the connector. It read 12.8 volts. While still conected i moved the wire around only to find the viltage drop to zero. There was my problem!!! The wire was actually broken inside the insulation!! When the wire moved a certain way it would completely lose connection and cause an open circuit! I fixed it temporarily by cutting the wire back and soldering it on to the pin before reassembling the connector. Problem is fixed. Figured I would share my story to save someone from the grief of trying to find this problem. In all the years I have been working on cars I have never come across a wire that was broken inside the insulation. From looking around I found a replacement plug made by dorman. Part #645-595. Its a universal plug that fits a variety of things on GM vehicles. I plan on buying that and completely splicing it in so I have a brand new plug.
