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bill, dodge master tech
Category: Dodge
Satisfied Customers: 1630
Experience:  25 years with dodge drivability and electrical expert
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2004.5 dodge cummins 5.9 with ohm meter on 200 I get .8 ohms

Customer Question

2004.5 dodge cummins 5.9 with ohm meter on 200 I get .8 ohms at the end of wiring harness going to ecm (where the injector harness plugs into main wiring harness) probing two of the wires on the same group of injectors. probing group A and C but probing group B I get no reading. I unpluged ecm and probed pin to injector harness and get .8 ohms on all cylinders . Truck has miss on both 3 and 4. injector 4 reads 0 ohms all other injectors read .4 ohms. Bad ecm short out my #4 injector?
Submitted: 2 years ago.
Category: Dodge
Expert:  bill replied 2 years ago.
hi i'm bill
welcome to just answer
please remember I am NOT there in front of you! my answers are based on your information
an open in the injector circuit is USUALLY a bad valve cover gasket, YES the valve cover gasket, you see it has the injector wiring molded into it and over time the wiring gets brittle and crack, if you haven't already done so I would pull the valve cover and check the wiring from the plug on the engine to the injector and see if it is open, if so replace the valve cover gasket
Customer: replied 2 years ago.
I have removed valve cover and inspected all wires. Ohm out fine. I attached a photo of the problem i am having. There are three groups of wires going from the injector wiring harness down to the ecm/pcm. I will get .4 ohms of resistance on 1,2 and 5,6 but 0 on 3,4 this is the wire bunch that goes down to the ecm/pcm. When I unhook my ecm/pcm and probe each end of the wire from injector harness side down to ecm/pcm side I got 4 ohms on all 6 injector wires. My question is why do I not get the .4 ohms like I have pictured on cyl. 3,4. (Note picture is when wires are plugged into ecm/pcm. To me it is saying I do not have a full circuit in my ecm going to 3,4
Expert:  bill replied 2 years ago.
looks like you are trying to test the wiring with the ecm still connected, that's WRONG and can damage the ecm, to check the wiring you need to have the ecm unplugged and check at 1 probe on the ecm side and the other at the end of the harness,you cannot check wires with the ecm plugged in (that's how your picture looks) the way I would do it is unplug the ecm, and the injector, leaving the harness plugged in to the connector at the valve cover,and connect one probe to one injector wire and the other to the proper terminal on the ecm plug, if the reading is anything greater than 5 ohms that circuit is suspect, if you are throwing injector circuit codes it is 99% the valve cover gasket OR the female plug on the gasket the pins can spread,, remember the ecm uses a 48 volt driver to fire off the injector, so you cannot test the ecm output with a 12 volt test light
Customer: replied 2 years ago.
How Do I test the ecm. Doesn't seem to be out putting any voltage. All injector wiring ohms out fine.
Expert:  bill replied 2 years ago.
without a scan tool you cannot unless you have a test light that can handle the higher voltage the ecm puts out to fire off the injectors.
what are the exact codes you are pulling so I can pull the diag sheets
Customer: replied 2 years ago.
Expert:  bill replied 2 years ago.
here are 2 links 1 is for the diag procedure for the code you have, in case you do not have it, the second is from the tech help desk (engineering dept) and gives a specific procedure to test the wiring using a HEADLAMP to put a load on the circuit, since the valve cover gasket and wiring can ohm out just fine you need to put a load on the circuit to see if wire can carry current, and remember the wires in the valve cover gasket can be broken internally and open with the cover on as the torque of the cover will compress the wiring.