i have a 1999 dodge 3500 diesel with 5 speed tranny 144000 miles im lost to what could be wrong with my truck its been very hard to start it takes about 10 to 20 seconds then fires off check engine light came on and got 4 codes i know what the codes are po122,po237,po336,p1689 i have allready looked the codes up it dosent sound right that 3 sensors and the injection pump comm. to ecm i dont think all the sensors would go out at the same time im starting to think my pcm is going

 

check your fuel pressure coming into you injection pump from the lift pump. usually when you get any communication error codes from the injection pump it is the pump itself going bad a very very common problem with the 24v cummins.

 

i have a fuel pressure gage when the truck is running at idel its at 21psi and i know about the ecm comm. problem can meen the pump is going bad but i dont think that the map,crank,throttle sensor would go bad at the same time and the funny thing is after i deleted the codes the truck fires on the second crank now

 

i would check and clean all of your grounds! could have one dirty. also pull the connectors off and clean them up put some dielectric grease in them and reinstall. that will help with moisture.

 

i replaced all battery cables and cleaned all the terminals last week when it started acting like it was trying to start off only one battery and have tested both batterys at schucks there fine

 

not the posts on the batteries but the grounds to the engine and everywhere else, they can cause funny things to happen