I'm helping a friend who's working on a 1995 dodge 2500 ram that has not spark. He has replace the cam and crank sensor. no spark. I went out last night and checked voltage to both sensors -- 8.8v. I ohmed the wires to each sensor. pin 7 of the ecm conn showed 001 ohm pin 24 showed 657 ohms. I put 12v to the wires pin 7 showed 12v and would light and hold a head light. pin 24 showed 12v but wouldn't carry a load. one thing I don't understand is that we show a green wire pin 7 but changes to orange at conn. pin 24 shows yellow but changes to green. we can't find a circuit diag being it is a 95 model. can you help us out here? If we had a correct wiring diag I think I could figure it out. thanks , tom. I retired from Int'l after 40 yrs of working on semi's.
Welcome to JA!
Sorry to hear your having problems. What Engine is installed in your friends Truck?
Also, are there any Trouble Codes?
I have the entire Ignition system wiring diagram for.
can you send it and if so I need to know what voltages at what stage.
Yes I am uploading it now :)
I will check if Voltages are included
thanks. what about the color change in the wiring?
Yes colors are included
This is the Diagram..let me see if I can find Voltages
what about the 657 ohm resistance? does that sound like a bad wire or does it go through a relayor resistor?
I am looking now :)
it does display a code for no engine crank. If I am right the ecm needs to see the engine turning over to power up the other systems. is that correct?
The Crank and Cam sensors are Powered and Maintained by the PCM.
I am trying to locate a power chart for that Connector :)
A quick note...
Check the ASD Relay in the Fuse Panel. "Auto Shut Down" It can cause this too.
we have changed that , no difference. I checked pin 30 - 12v. pin 86 12v pin 85 - 12v. any relay I ever worked with pin
85 was usually grnd
You may have received a bad Sensor too. I am uploading a test for the new crank sensor now :)
we have replaced the sensor with another new but no diff.
Did it just stop running or it wouldn't start next day?
from what I was told it progressively got worse until it wouldn't start at all. the diag come through but I am having
trouble printing them.
Sorry about that
Sorry I can locate Voltages for some reason :(
Still looking tho
when I found the wire color change last night I ohmed the wires from pin 7 to 24 with everything unplugged to see if
they were shorted and they wer not
If the Crank sensor is good and there is no shorts then I suspect a Bad PCM. That would explain the slowly getting worse. A faulty Crank sensor would have made it stop instantly.
But just to be safe,..has the Engine or Transmission been removed lately?
we didn't want to change it without checking it first. can you send me 60 pin conn with ign and batt voltages that
could be checked befre we change it out.
Let me see what I can find :)
if we have batt voltages and ign in the correct spots than I would agree. not that I don't I always hated to condemn the ecm on the trucks because they were 2-3000.
I don't think anything has been change it just quit.
60 Way Connector
Have you checked the Coil and Distributor yet?
I was talking with Harvey and told to check pin 3 and pin 9 with our headlight. the dist has a new sensor in it and the coil is not powering up but the relay won't close if you can't see cranking -- correct?
I think thats backwards. The relay should be Open in the Run and Start position and Closed during Key off.
A noticeable click can be felt.
when the key is turned does it power it up? I mentioned that pin 30 has 12v all the time -- normal. pin 87 12v but I also noticed pin 85 had 12v to it which I don't think is correct. I thought pin 85 was usually grnd.
I am not sure without the Chart.
The PCM only has 60 pins. Where are you getting number above that?
the numbers are off of the relay themselves. I was checking the conn in the pdc center
Ohh.... I see. That could explain it then lol
Ahh,... The PCM Controls the Ground for certian devices such as the Crank and Cam Sensors. If there is an Internal fault it can put ground to the wrong pins on the relays.
page 11 of the wiring diag show the auto relay. I don't know where the two splices go.
Let me look
Terminal 85 is Grounded by the PCM, I just found that and thought I would tell you.
So if it has Power then you have a short in the PCM.
o.k. could you grnd pin 85 to see if it would start?
Thats a good question. If you ground it out and it has 12v going thru it, it may fry the PCM. Not sure tho. Try that at your own risk :)
is pin 51 of the 60 pin conn my grnd? I can check that.
I would take pin 51 out of the conn and than grnd it.
pin 51 you said was grnd so it shouldn't have power to it -- correct if that is so grnding it should cause an issue
Pin 51 is the Shutdown signal. Witch probably just closes the Ground.
it shouldn't cause an issue
if I am understanding you right the relay doesn't power up or does it power up all the time. if pin 51 grnds to shut it off than it would act like a normally close relay wouldn't it?
Kind of,The PCM Powers the Relay up thru pin 57. Then uses the Ground to Close the signal. I found a diagram that explains it.
can I see it?
Of course you can :)
I will be back in 5 minutes. :)
I will remain here in the chat :)
I wonder if we have a wire shorted under the pdc. I need to go back out there tomorrow and check it out. I sould be able to remove the 60 pin conn and power up pin 57. if I show power on pin 51 than I have a harness issue and if not it is like you said earlier the ecm in bad.
I need to save this chat and contact you tomorrow. I would like to print our chat -- is that possible?
You should be able to print this chat yes. Press the CtrL key and P. Or just bookmark this page "Add to Favorites" as you can return to it any time you need. I agree with the method you mentioned :)
Just return to this page with any further questions :)
thanks for your help. I will tell you tomorrow what I found out but it wouldn't be until 7P.M. when do I rate our time
You can wait until we figure it out to Rate or you can Rate now. Either way. I will still continue to assist even after you Rate. I am on all day and most of the night so anytime is good with me :)
You are very welcome.
thanks again , tom
with the wiring diagrams that you sent me we were able to trace down the grnd wire for pin 4 of the 60
pin conn and found it rotted out where it ties into the splice for the grnds. repaired it and it starts fine. thanks again