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My truck is dead with an error code of 1689 (ECM communication failure). I replaced the lift pump, VP44 inj pump and the ECM. No resolution.

I believe that the failure is in the wiring harness. This is the harness that wires the ECM (right side of block under fuel filter) to the lift pump, fuel inj pump, grounds and other sensors.

Before I replaced the ECM I did not have power to the lift pump and 8v on coil side of fuel sys relay. With the new ECM the lift pump runs properly.

Had a poor ground that I fixed. I also replaced the fuel pump relay.
I keep running into dead ends....

Need help.

Matt
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1999 5.9L 3500, 6-Speed, 355 Rear, Edge EZ, 4" MBRP exhaust, Exhaust Brake.
Cracked 53 that has been patched and sealed!

 

Not sure what to tell you but there is no fuel pump relay. The fuel pump is powered direct from the ecm. Do you have a factory fsm to trace the circuits?

 

I helped fix the same thing you have going on.go to your fuel relay and with the key in the on pos move the relay side to side and see if it makes a clicking sound if it does pull it out and with a small screwdriver bend the conncters that the relay plugs into and that will make better connection and your truck should start.seems simple I know .but if that is lose the ecm gets no power and will not talk to the inj.pump and give 1689 code.good luck let me know how it goes.

 

The relay was not plugged into the correct spot.

Before I took the truck to the dealership for a new ECM (the 2nd time) we were trouble shooting the electrical issues and the relay was put into the wrong spot.
Once the new ECM was installed I got the 1689 code again. I tore the wire harness apart from the ECM to the inj pump. Everything was solid! That is when I focused on the relay (more so on the wire from the ECM to the relay and back to the inj pump). That is when I noticed that the relay was not in the socket!

relay installed, injectors bled and the truck started!

I have noticed that it is less sluggish since I installed the BlueChip inj pump and a new ECM. Either the ECM or the old inj pump was dieing. Life is good now that I am back on the road!

Thanks for the suggestions! Too bad the ECM was actually the problem.
I will look to sell the truck next year and upgrade. Maybe someone will want a "project" truck!?