major code prob w/ detroit

I have been having a heck of a time trying to diagnose a problem I have. 3 weeks ago while driving 1300 rpm's about 50 m.p.h. I noticed the truck had felt like it lost some power. I had the cruise on & the speed dropped real slow. did not surge or do anything you could feel. kinda felt like I was climbing a very steep hill. I press the go pedal & nothing, then I down shift & it picks up o.k. got to unload 2 miles ahead. no problem for the next 130 miles, then same thing happened. took to a local shop, showing all sorts of codes. he thought it may be a bad oil press sensor, so he unplugged it.I told him to program the truck so it will not shut down, he did. I drove 3000 miles & no problem until just last night. started again. cruising along then I feel the truck slow, it does not slow as if there is no power, it just holds at a certain speed & I put the pedal to the floor & nothing, then it gradually drops speed & rpm, but very slowly, then I downshift. limp to where ever & start over. the 3 times it happened was just before I made it to my unload destination. I looked up the codes when I got home tonight. the codes the truck display are 34-36 given by the (red) engine stop light the following by the yellow engine warning light 14-23-45-54 all batteries are new. all cables & jumpers are new all ground wire, cable everywhere was taken off & cleaned down to bare metal. 1995 11.1 ser 60 detroit. any one have any idea's ? I mentioned the e.c.m. to the shop, but he said it would throw a code 56 if it were the e.c.m. I'm lost on this one. hot from e.c.m. & ground all new too.

 

where, how do I check the 5 v sensor supply ? just left the detroit shop. guy told me to replace oil pressure sensor & boost pressure sensor. I am not that smart, but I do think for myself & not just what a comp tells me. I know it is throwing the codes, I told him, but all those things are not going wrong with the truck at the same time, nor can ALL those sensors go bad all at once. I know if truck is running hot, e.t.c. coolant is fine on temp & level, as is oil. it has to be of electrical nature, I think. will take e.c.m. off this wknd & inspect all wiring. thanks for the advice. if ya can think of anything else, let me know. thanks guy's.

 

You have a lot of engine sensor voltage codes. Could indicate wiring faults in the engine sensor harness. this makes sense to me. I am getting a lot of engine sensor voltage codes.

 

Things just got worse. I talked to my detroit man & he said he does not have time to do any work on it, but he can hook up to comp. showed the codes I mentioned here. he recommended I change the oil pressure sensor. I don't see how that would fix the problem? he mentioned if the sensor shorts out, it could send fault codes thru the sys. I said o.k. that makes sense, but we unplugged the oil pressure sensor last week to see if my prob would still be there. we still have the problem. but he still thought a new sensor hooked back up would change things.

also the boost sensor he said was showing a code. it is the plastic module that has g.m. stamped on it & screws into the manifold on drivers side. sole me both sensors today for $100.00 h told me to just take & try them out first, but I like to pay upfront, now I wish I would of waited on the payment. NOW here is how things got worse... got truck home let cool off & replaced the 2 sensors, which I thought in my mind was not the problem, after replacing them, I looked at the hot & ground from battery going to 1 plug in on e.c.m. looks simple not a lot of wires just 2 from battery to one plug in. inspected everything from comp to battery & all battery cables, e.t.c. took off alt hot/ground, checked cleaned. all o.k. checked bottom plug in on e.c.m. in the front facing the front bumper, wiggled around looked at them real close, could not see anything wrong, no corrosion, no frayed places on wire. nothing got my attention as abnormal.



so I start truck up. it runs up to 900 rpm. I cannot get idle to drop at all after about 10 minutes the idle kicks down at the exact same time, the engine fan kicks on & the engine warning light comes on. I shut truck off for a minute, start back up it immd goes to 900 rpm for approx 10 min then the the high idle kicks off & the fan comes on & engine light comes back on. this I did 8 times. always the same cannot get to idle lower no matter what. I tried to move every wire I can while at high idle to see if I can make a change by moving a loose connection or something. what gets me is the truck ran fine after the brief power loss yesterday. ran fine to the shop 40 miles away & back, this new problem only happened since I took a look at the wiring sys & put it right back just like it was. I just don't want to have a shop throw parts at it. I could get a new or used e.c.m., but dont want to if that does not solve the problem. or a whole new wiring harness either. I would buy both if that was the cause. it's the proper diagnosis that I need. I still get the same codes. so NOW.. what would make my truck idle at 900 & not drop at all for 10 min & then kick off idle & engine fan come on & engine light? it has to be electrical? it has to be something I touched, caused this new problem was not present before. H.E.L.P. tell me exactly what to do, & if it works I'll send you the check.