Check this out, never heard of this. Scroll down to almost the bottom of the page.
http://hoeslidiesel.com/store/page2.html
Connector,VP44 Injection Pump
Repair connector for the VP44 injection pump. Fault code P1689(no communication between VP44 and ECM) is a common problem when this harness goes bad. Pins in this connector can wear out and not seat properly to VP44 pins. Why replace the entire $1,000.00 engine harness when you can replace the connector?