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?

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?

Thanks, buddy! I had this code occur to me when I was having the other code fiasco happen. It has not happened again since, so I dunno whats going on. But, will take note about this if it does so occur again.

Quite interesting! Maybe someone can be a guinea pig when they get this?

kinda similar to mikes relay observation (effectively a circuit issue) http://www.cumminsforum.com/forum/98-5-02-technical-diagnostics/116431-p1689-error-code-cause-code-found.html

i wonder if a guy could buy just pins, so he didn't have the splice there.

Hello all. My buddy's truck had the same problem. Recommend taking out the fuel system relay and hook a test light to the hot battery terminal. Probe #85 cavity for that system. Gonna be the top left spot. The light should be bright. If it's not bright, open up the PDC box and splice that ground into a GOOD ground; such as your battery. Relay has a bad ground, doesn't energize fully, and you have problems. Worked on his truck. Hope this can help save someone a lot of time and money.