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FICM voltage VERIFIED at injector wires

Injector Voltage

18K views 46 replies 16 participants last post by  6.0cj7 
#1 · (Edited by Moderator)


I would ask anyone who feels comfortable enough with a voltmeter to probe 2 wires on their engine to do so, and fill out the poll with the results.

"How to check the voltage AT the injector harness"

1. Engine off, Key out of ignition

2. Pick any injector, and unplug the wiring harness at the valvecover by pushing in on the metal retainer and pulling the (engine side) harness away from the plug. (pictured above)

3. the pin locations on the harness (pictured) are 1 & 3 are power, and 2 & 4 are grounds.

4. Set your voltmeter to "DC" voltage.

5.. Put one lead of your voltmeter into pin #1 (or #3), and connect the other lead of the voltmeter to ground BUT NOT THE GROUND IN THE HARNESS. Go to any engine ground, anywhere on the block or head, or to the negative post on your battery.

6. Prepare to start the engine by making SURE that nothing you have put on or around the engine can get wrapped up in a belt, fan, etc.

7. Start the engine, and record the voltage shown on the voltmeter.

8. Turn off the engine, and return the wiring to stock.

9. Please come back here and fill out the poll.


Anyone with a scantool (or AutoEnginuity) should compare the value shown under "FICM Voltage" with the reading you took with your voltmeter...

Please DO NOT fill out this poll by simply reading a scantool for "FICM Voltage"...verify the voltage at the injector harness.

***
Starting your engine with one injector disconnected WILL set a code for #___ injector fault, but once the injector is plugged back in, the truck will run normally, with no check engine light or performance loss.

thanks~

Dave

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OK, just an update...

It looks like the signals are being "averaged" when you use a voltmeter...so if you see 10Vdc on the voltmeter you will have ~ 20Vdc in reality (confirmed with an oscilloscope).

So if you don't have an o'scope to capture the signals, then (roughly) double what you see with the voltmeter.

Since all of our previous testing was actually done with an oscilloscope, the voltages I requested are accurate...so just double what you see with your voltmeter, and fill out the poll.

thanks~

Dave
 
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#2 ·
What the heck are you posting up here for? :poke: :D

.
 
#8 ·
Hmm, well you've got me curious. I'll get one of my minions to do the voltage test tomorrow. :D My '04 and our '05 should be here. So how would one go about upping the voltage at the injector wires? :poke: This would be sort of like an idm mod for 6.0's?
 
#9 ·
Yes, there's a way.

But what this voltage test is about, is that we are seeing higher injector failures on trucks with low voltage FICM outputs to the injectors.

I spoke with a customer today, recently out of factory warranty, who has had nearly 2 dozen injectors replaced over the last 3 years.

He is an electrician, and I had him check his voltage at the injector harness...

10.1 Vdc :eek:

had a truck yesterday come in with (factory) injector problems and his FICM output voltage was 22, another one this week had 19, and 2 trucks came in for "hot rod" parts (not general repair), and they were both exceeding 40 Vdc, before & after we swapped in a set of larger injectors.

Since this doesn't seem that the injector itself (or wiring issues) is drawing an excessive amount of amps (which would reduced voltage)...

it seems that there is a huge disparity in FICM output voltage to the injector solenoids...and a corresponding disparity in engine performance.
 
#10 ·
Well hook me up dangit! :D

I wonder if the recent FICM tuning that's been going on addresses this in any way?

.
 
#14 ·
By replacing the FICM if I understand Dave right or maybe he has a new modification in the works?
 
#18 ·
OK, just an update...

It looks like the signals are being "averaged" when you use a voltmeter...so if you see 10Vdc on the voltmeter you will have ~ 20Vdc in reality (confirmed with an oscilloscope).

So if you don't have an o'scope to capture the signals, then (roughly) double what you see with the voltmeter.

Since all of our previous testing was actually done with an oscilloscope, the voltages I requested are accurate...so just double what you see with your voltmeter, and fill out the poll.

thanks~

Dave
 
#23 ·
Alright, I checked mine but I didn't post in the poll because I have some odd results I think. Did as the directions said except didn't put the positive end of the meter in the plug 'til after I started the truck since I'm by myself.

Plugged it in the number 1 position on the plug and the meter acted like it was scanning for something but never registered anything. Put it in the number 3 position of the plug and it read ~6.3V on the meter.

Does it have to be in the plug when you start the truck? Had the ground hooked to the truck battery. Was using the plug on the passenger side, 2nd one back from the radiator side of the motor.

Meter is a Fluke 7-600 Automatic Selection fwiw.

I'm gonna try it again tomorrow on a different plug and with a different meter.

.
 
#24 ·
This may be something that has to be checked with a freaking oscilloscope...I was hoping to get consistent results with a voltmeter...but I'm not sure that's going to happen.

try redoing the test once the truck is up to temp...see if it jumps up to ~20Vdc on the voltmeter.

:doh:
 
#46 ·
Where'd you get it from and how much was it? I'm looking around online but those things seem expensive.
 
#34 ·
Hmm, why don't you go ahead and send me that one in the mean time? :poke: :D
 
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