When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I would change the sensors, is cheaper than searching the fault. Because I don't think that the wire have a problem, But go all sensors to one plug ? or have all sensor their own wire ?
If they go to one plug check the connection
Get a can of electrical connection cleaner, some dielectric grease, a towel, a creeper and a light and crawl under the bumper. (safety glasses too)
Remove each plug, check for corrosion, clean as needed, then repack with dielectric grease. A small screw driver may be helpful. Be patient and wipe off crud first.
Check the connection of the sensor array to the harness (beside the spare tire)
Test.
Check dash defeat switch.
Any single connectio failure will defeat the whole system.