× Auto Repair Pros Member Benefits TechHelp Knowledge Base Forums Resources My iATN Marketplace Chat Pricing About Us Join Industry Sponsors Video Members Only Repair Shops Auto Pro Careers Auto Pro Reviews
Join Now
International Automotive Technicians Network
6.0L Misfire with Injector Circuit DTCs
Posted to HD/Fleet Forum on 8/18/2011 23 Replies

This ambulance came in with a running rough concern. I first pulled DTCs and found P0262 & P0265 (#1 & #2 injector circuit high). I performed a KOEO Injector Electrical self-test got this: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Scan Data]

This is the power balance: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Scan Data]

FICM voltage PIDs: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Scan Data]

I looked up the pinpoint test for the DTCs. The testing involved checking the suspect injector for circuits shorted to each other, injector circuits shorted to ground, injector circuits shorted to power, and suspect injector coil resistance. All of the steps passed and the pinpoint test directed to replace the FICM.

I've encounter this issue before. I've replaced FICMs for this very issue because that's what my diag steps led to. However, in the past, the $700.00 FICM did not fix the concern. I rarely see a FICM fail on an E-series. Usually, on a E-series, some issue with wiring harness or injector was the cause.

The 6.0L injectors have an Open Coil & a Close Coil. These coils control the position of the spool valve inside the injector. These injectors also operate at around 48 volts. In my experience, these "high voltage" systems are more sensitive to circuit failures than what I'm used to at battery voltage level.

Per the pinpoint tests, circuit checks are performed by using an Ohm meter. I'm sure we all know how accurate that can be. An ohm meter can be useful and does have its place, but you also have to understand those "tests" do have their limits. Both injector coils have a resistance spec of 0.4 - 0.6 ohms at ambient temp (which is the temp my testing was done). Unfortunately, I have an injector circuit fault on the most difficult injector to access. Fortunately, the FICM is easy to access on a E-series. Here it is: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Photo]

My circuit tests was done at C1388a. From there, I can measure the entire resistance of both #1 injector circuit coils. I measured 0.7 ohms. This technically is out of spec, but I'm also testing resistance of additional wiring. I compared this to a normally functioning injector (#6) and measured the same thing. So now is the time to try something different.

I looked through the waveform archives to try and find known good injector waveforms; I didn't come up with much. I started by testing a known good injector, #6.

Open Coil: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Open Coil with measurements: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Close Coil: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Close Coil with measurements: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Close Coil zoomed out: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

This is what I got from the misfiring injector (#1)

Open Coil: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Open Coil with measurements: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Close Coil: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Close Coil with measurements: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

Close Coil zoomed out: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Waveform]

By looking at the coil ramp, it looks like both coils on #1 injector are shorted. It appears current to getting excessive too fast and the FICM is turning off the voltage. Unplugging C1388a at the FICM would basically be disconnecting #1, #4, #6, #7 injectors since only those injector circuits are going through that connector. I unplugged C1388a and reran the KOEO Injector Electrical self-test; it return with injector circuit low (instead of circuit high) DTCs for those injectors. This tells me that my FICM is good and not causing the short.

If my circuits were shorted to ground or each other, I would expect current to immediately peak and not attempt to ramp up. The current waveform looked like a typical shorted coil winding even though the resistance test for both coils pass. Based on this, I determine the fuel injector coils are pulling too much current, so I get one from our parts department. Before I install it, I took it out the box, plugged it in to the engine harness, and reran the KOEO Injector Electrical self-test and got this: [2005 Ford E-450 Super Duty, ECM/Inputs/Outputs Scan Data] Notice this took care of P0265 also.

Maybe this will help someone. I'm open to any comments, critiquing, experiences, discussion, etc.

Robby from Alabama

Files Referenced:

thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail thumbnail

23 Replies Received (View Replies)

 

car Vehicle Data

2005 Ford E-450 Super Duty 6.0L Misfire

Engine6.0 L
Trans4-speed Automatic (Electronic)
SymptomsMisfire

car Vehicle Data

2005 Ford E-450 Super Duty 6.0L Misfire

Engine6.0 L
Trans4-speed Automatic (Electronic)
SymptomsMisfire