I just finished installing a regulated return on my truck, the 50 cent mod, new glow plugs, and a new injector wiring harness on the drivers side. The 50 cent mod was done in hopes to relive an engine miss/shudder but when I got under the valve covers I found the connections were as tight and snug as could be. However, I did replace the drivers side injector wiring harness since the clip was broken off.

After putting it all together and starting the engine, it ran smoother, quieter, and the miss/shudder was less pronounced. Over the past several months I've replaced the ICP, IPR, CPS, Throttle pedal assembly, Exhaust back pressure sensor, installed a PMT1, performed the In-tank modification, installed an AirDog, ITP regulated return, replaced fuel filter, intake air temp sensor, engine oil temp sensor, and HPX crossover tube. I still have this slight engine miss/shudder/stutter and I don't know what's causing it.

Anyway, I decided to hook up Autoenginuity tonight after the RR, glow plug, 50 cent mod install and I came up with a P1668 only after running the cylinder contribution test 2 times consecutively. Now I try to run it again and I can't get it to give me that code again. Does the P1668 PCM/IDM Communications Error indicate my IDM may be going out and would an IDM that is not working right be the cause of the slight engine miss/shudder/stutter?

Thanks for any ideas on this.
Drake

 

most of the time the IDM works or it dont..have you checked for chaffed wires from rubbing on the VC's or stuff down in the valley?? how long ago was the fuel mods done??

 

It might be one of those time when an odd code shows up. IIRC, others on here will have a code show up if they run certain tests a number of times like you did. If it doesn't come up when you scan for codes on the first page, I wouldn't worry much at this time.