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Discussion Starter · #22 · (Edited)
So some updated news. I swapped a working pcm and ecm, no change. Had shop Check VP44, dash gauge cluster and fuel pressure to verify everything was correct. All was good. Then found #8 and #10 pin were crossed and were sending the oil pressure sensor to the tack and vise versa. Got those switched and all gauges on dash work now... all wasfor 10-20 mins. Then it started trying to run away again. (Gauges still work though)And a dead pedal type issue and bucking. Pulled codes with a good scanner and was able to get these and test the APPS and TPS. Both went 0 to 100. Voltage output regulator putting out 13.7Vs. Cleared codes and watched codes shoot up the moment we touched the throttle. Turned the truck off and then fired ot up and it kept randomly reving. We got the same codes they got before all the no bus codes i was getting. Now im not getting any no bus codes ..... why the hell would crossing those 2 oil/tack wires get rid of all those codes?? Also if they did it on purpose who the **** would know that would happen?
 

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Those tow wires being switched, Where exactly was that? That is really strange. Sounds like somebody ahs really scrfrewed up the wiring inad computers. You or some mechanic? Previous owner?
 

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What year or Part number ECM did you switch to. Where did you get it?
 

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Discussion Starter · #25 ·
All the wiring was done by the previous owners mechanic. The splicing and switching of these two were done at the ecm. The ecm I switched to was out of a 2000 24v auto. Not sure on part number but i just swapped to it to see if any of the codes changed. Now that the codes have changed ill reswap the pcm and ecm again and see if it changes or clears the codes. Im thinking the voltage regulator inside the pcm is busted.
 

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Discussion Starter · #27 ·
More development in this sogga... when cold, nothing happens... when hot starts acting up.... now... when hot, I pour cold water on the ECM.... truck runs correctly.... give it 2 mins, will act up, can repeat process all day.
 

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That is often due to bad solder connections inside the ECM for the switchover to low lead solder 20 years ago. If testing by swapping ECM's they have to be the same Cummins PN on a sticker usually on the back side of it. 98.5 and 99 are all the same, and from other years do not work.
Yes regulator is in the PCM but not related dto ECM or running so long as voltage is over 12v.
 

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Discussion Starter · #29 ·
That is often due to bad solder connections inside the ECM for the switchover to low lead solder 20 years ago. If testing by swapping ECM's they have to be the same Cummins PN on a sticker usually on the back side of it. 98.5 and 99 are all the same, and from other years do not work.
Yes regulator is in the PCM but not related dto ECM or running so long as voltage is over 12v.
So, wait.. if the voltage regulator is in the pcm and not in the ECM. Then changing ECM wouldnt have any effect on any of the voltage outputs? So id still be screwed?
 

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The PCM is the regulator that supplies and regulates the voltage only to the alternator parts to charge the batteries.

The ECM supplies(charges systems) with juice from the batteries to run most systems rdelated to the running of the turck and fuel system. In other words the ECM is the switches thatturns everything and supplies voltage to all sensors, compouters and chips related to the engine and the lift pump. If voltage is low to a sensor it is because it is not being supplied well due to ECM failure or other shorts. If battereis are bad or not being charged well from the alternator the ECM can not properly supply those systems. Not enough juice coming in, not enough going out to sensors and systems.

Understand better now.
 

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ECM's and other circuit boards on these trucks of the era suffered from Heat Cycle issues where after so many run cycles of the curcuits warming up the expsansion and contraction would come loose due to the bad solder. Thus ECM failure.
 

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Discussion Starter · #32 ·
Ok. So I got the ECM rebuilt. They said everything looked good except for 1pin was bad. They said they fixed it but didn't give me a pin number or a picture. Got it back a month later and popped it in. Worked great. Its a great truck when its running, tranny seems really strong too. Cranked it up the next day. Same issues as before. 5V system being weird. Giant delay in throttle. And takes forever to roll forward. So I took out the ECM, and put it in a fridge to see if cooling it off would work like before. And it didn't. So I took it apart VERY CAREFULLY and found this. I believe its #5 wire which is the keyswitch signal wire. Or if the diagram I got is mirrored its #6 which is oil pressure sensor wire.. Would this really be the issue?
 

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Have you tested that pin with a multimeter?
 

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No, you would do this while the ECM is out of the truck. You can test Pin #5 for continuity and resistance, and make some inferences from that.
 

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Discussion Starter · #36 ·
No, you would do this while the ECM is out of the truck. You can test Pin #5 for continuity and resistance, and make some inferences from that.
Oh ok. Thanks. I don't know **** about 12v. Still learning this side of mechanical repairs.
 

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No problem! That should give you some information about the solder condition of that pin, because it definitely looks different from its neighbors- as you have indicated.
 

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I assume the soldered connection on the board you have indicated with an arrow above is the physical back of the male Pin #5 you also have indicated with an arrow?
 
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