24v Limp Mode; max 1400 rpm

[Layne Merritt]

I took my 98.5 2500 out of the barn last weekend; I had a batteryminder on it all winter (Alabama winter). It started fine and drove away; after about 2 miles, the CEL light came on and now it won't go above 1400 rpm. It starts and idles fine. Codes: P1689 with the P1693 companion code. I confirmed continuity of the harness between the VP44 and the ECM with a multimeter. The plugs are clean; first time they've ever been off. All the grounding wires I can find are snug and I switched the fuel system relay with others in the box. No change.

I don't want to replace expensive parts without a confirmed kill. Any suggestions?

 

[Bromiley99]

By far the best site to use when diagnosing a VP44.
https://www.bluechipdiesel.com/troubleshooting-1

 

[Ozymandias]

Problem seems solved in a different Thread.

https://www.turbodieselregister.com/threads/24-valve-max-1300-rpms.265140/

 

[Layne Merritt]

Update: I finished replacing the VP44 tonight and all went well. I took it for a short test drive and everything seemed normal. I will take it for a longer drive tomorrow and get the codes cleared.