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code p1278, not the wiring, IDM or PCM

23K views 9 replies 3 participants last post by  7.3coal roller 
#1 ·
So I finally fixed all my codes except the p1316. I was able to get my hands on a good scanner and did a koeo test which popped a code P1278. I did some research and everything said injector wiring and to ohm everything and find the bad wire. The problem is everything test the same. All eight injectors test 3.3-3.4 ohms. I even pulled the fender and tested there and I get the same thing on all injector circuits. So the next things were the IDM so I changes that with one I know works from one of the trucks at my work. Same missfire. So I thought maybe the PCM or ECU and swapped that while leaving the known good IDM in. Still the engine misses and gives the same code. What am I missing here?
 
#6 ·
Less than 5 ohms is what you want. I used a fluke tester(good brand) and mine where all 3.3-3.4ohm. You want to check from the common pin with one lead and use the other lead to check the two connections to the left and right of the connector. the last two on each end are the glow plugs.

If those test good then you need to check the ohms at the engine harness and then if that checks good you need to check the ohms at the IDM. Your dealership can get your diagrams of which pins to check or if nessary I can get you at least the one for the IDM.
 
#7 ·
Thank you! My IDM checks out good, per ford. My thread is below this. I'm pulling valve covers off tom, if above 5 ohms it would only be the harness? Like the injectors don't affect the resistance at all? (sorry for kinda jacking your thread)
 
#8 ·
If you check the OHMs at the valve cover harness and they are high then it is either the harness or the injectors. If they are high then you should pull the valve covers and check for harness problems. If there are any problems, or if they look original then you should replace the harness. You should also check the injector OHM to verify that it is just the harness and not the injector. If it is the injector then you must replace the injector.
 
#10 ·
FYI.....
there could be one strand of wire inside a circuit that is good which will provide good OHM readings. The proper way to test a circuit is with a load test and voltage drop. Use a suitable bulb, fused power, and a known good ground. If possible, manipulate the harness and monitor the bulb for any flickering or dimming. There should be no more than .3V lost across the circuit with the load applied.
 
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