I originally posted in the performance forum since I have so moany mods.

Symptons:
Truck Starts fine both cold and hot.
When cold engine and guages work great, just a slight miss. As engine warms up engine starts to miss badly, cutting to idle, eventually the oil pressure guage drops out. At that point throttle is very laggy, with no power or RPM limit(seemingly). It does have oil pressure, just not indicating it. Periodically the oil pressure guage will work, and the throttle response will be normal.

I have a 1693 code. Check engine light is on and when the oil pressure drops the chck guages light comes on.

Done so far.
Removed, cleaned and reattached all grounds.
Reset APPS
Disconnected computer
Disconnected alternater, and had it tested at a rebuild shop.
Disconected Battery one at a time
Reconnected all plugs and sensor connections

None of these helped. Is there a way to read the Cummins Computer to see what the 1693 is for? Someone said a smarty would, but I want to make sure before I spend that kind of money. Dealer won't scan it since it is so modified. (think they would want business?)

Recently as I have been trying to test and find problems, I notice that it is taking a bit (30 to 60 seconds) for the battery to get up to 14V. I comfirmed this with my DVM at the battery.

I am starting to think the PCM died or is dieing.

I am going to replace my oil pressure sensor and order timbom's apps. I wouldn't think that the oil sender would effect throttle. Simularly I wouldn't think that if the APPS is bad it would effect oil pressure readings. Hence my thought that the common item to all of these issues is the PCM

Any help or ideas would greatly be appreciated.

 

Don't believe oil sensor will affect. More like the sensor circuit circuit. The ECM and sensors may be losing ground. Look carefully at ECM conn for corrosion, damaged terminals.

 

You will have to check the obd11 codes with a code reader first and see what other codes are between the pcm and ecm p1693 A companion DTC was set in both the ECM and PCM. Note if the tack is jumping also might be the cam shaft sensor below the vp44. But check the other codes first.

 

I checked the connection. But I will pull the ECM out tommorrow to look at the termination a little closer.
Tach is smooth and not acting funny. I had a cam sensor go bad before and it is not acting like that.

I didn't realize that a OBDII reader shows more codes than the dash odometer. Will read those codes tommorrow as well and post.

 

Ok. Similar behavior this morning, although it started to act up quicker as it was warming up.

Borrowed a reader with CAN-BUS capability. Had three codes, MAPS, Coolant temp, and TPS. Understood MAPS and Coolant as I had them disconnected for a stint. Cleared the codes.

Started truck and immediatley threw a P0122 (TPS Low Range).
Question is would a bad APPS drop all of the guages including oil. While watching the CAN-BUS not only does my oil guage drop to zero but the Man Pressure goes to 75"HG. Every once and a while the guages will read normal and the truck runs fine.
The coolant temp reads accurately and is un-effected. The IAT seems correct as well.

So back to a ground or weird failure of APPS. Is there any ground in particular that gives this kind of trouble?

 

maybe check the grounds from the motor to the frame and battery. if i am thinking right a lot of that stuff grounds to the motor. their could be a short somewhere on the ground straps

 

My 1st thought is an electrical component , that when it warms up fails , something as little as a resistor in a package / circuit board .
But with many of your devices giving odd responses it sounds like low voltage [ low voltage is usually caused by bad ground ] not the positive side .
Low voltage makes a lot of things act odd .
Start with some jumper wires at battery & at the computer , to see if symptoms go away , then if they do , finding which of many grounds is bad is tricky , a factory electrical component locater manual , should have a description of all electrical grounds , going through them one at a time , cleaning the surface & applying a dielectric grease .

 

Will try the jumper wire trick. When I redo the grounds I am using Copper Coat which will protect the connection over time.
I did pull the competer off and all connections look good, clean and have no bent pins. I assume that the comnputer case is its ground?
I did notice two "hot spots on the computer" Looked like the paint I put on it blisted. These are located top center.

I think I might have the electrical stuff on a file somewhere. So will start digging while the rain passes over. Figures, the truck always runs on a good day, when it breaks it is either pouring or snowing.

 

The computer is going to have several grounds , going through harness / wires , not that the case would be grounded .
The hot spots sound like you have an issue there .
Its common that if one of a few a grounds are lost , that the computer will find new ones , killing its self .
So if you do find a bad computer [ not common , but usually only happens when someone is doing something electrical , jumping , welding , ect. ] , then you need to find out why the unit failed , because putting in a new one with out fixing the why will also kill it .

 

John, Thanks for the input. You are correct, need to find the problem b4 replacing the ECM. Any easy way to tell that the ECM is bad?

I opened the ECM up carefully and found out that there is no "hot spot". Was hoping to also find a cold junction but nothing I could see and wasn't going to put a soldering iron to it. Luckly I was able to get it back together.

I have a solid 5v to sensors, now am trying to ring out pin 11 which is the return for all of the sensors back to the ecm. I also need to ring out pin 30/49 to the battery(-). I hate to pierce the wires in the harness but may have to to find this problem. Why not can't be any worse than opening up the computer.

 

Wires ring out fine. Good path back to battery on battery return. Sensor returns have no shorts and good continuity.
All grounds Identified on electrical schematic have been redone and wires checked.

Thanks for the help so far, ANy other ideas. Yes i did pull out the edge comp

 

To find the problem you need to check every pin on the computer & the harness , the tricky part is finding the bad one [ or more ] if there are any , with having the right info , when I had a breakout box the values for each connection [ both ECM & harness ] were in the book that came with it , it was not common info and I had lots of factory & pro-shop manuals [ Motor & Michell ] .
Then one of the normal things that has killed many computers have been on the actuator [ components that do things , controlled by computer ] that have coils in them , switches / valves , when they short out , that short can go back to the ECM & damage it .
To avoid piercing the wire , what is standard , is to remove some of the covers on the large connectors at the ECM & probe with a small pin to inside to the crimped end of wire .

 

Thanks,
This will be a slow process, but I don't see any other way except wire by wire. I will also have to try to find some of the manuals that have the not common info.

Maybe I should just P-pump it ;-)

 

Older Trucks The Crank Sensor Would Cause Probs Like That Do You Have A Crank Sensor If So Check That

 

Dealer gave me some reference voltages and resistances to check. All where correct.

Funny thing is today I couldn't get the truck to act up. Continuously throwing codes of 121,122,123.
What is different today is for one it is sunny and warmer(it is suppose to rain tommorrow so will have to wait till then and find the problem) FYI just kidding.
But I did have the ECM out of the truck since Sunday. Maybe it had an error and cleared?
I will replace the tpps, camshaft sensor, maps sensor and the oil pressure sensor. From my limited schematic the later three share the same 5v and all of them share the same return pin.

I am not sure if this is right but my MAP responds to boost but is reading standard atmosphere of 57"hg. At idle and when the engine is off. Anybody look at that before and is that correct?
I am replacing the tpps as it is throwing codes and I was able to get it to act funny (drop throttle) a couple of times. I was never able to get the oil pressure guage to drop to zero and maps to stick at 75"Hg

All of these sensors require a 5v supply from the ecm, so hopefully the pronlem is as simple as a bad sensor. The Dealer is getting me a little more info on voltages however, in case it doesn't work.