6.0L Misfire with Injector Circuit DTCs
Posted to HD/Fleet Forum on 8/18/2011
24 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