Fuel injector knock

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Trgglynn

Member
Jan 5, 2024
63
4
8
Portland, OR
2004LB7 said:
EfiLive won't give you any voltage or health information that can help you diagnose the FICM. What you need is an oscilloscope. A regular meter is a skilled user can do a lot but it won't show you the pulses and signals that are happening at the FICM pins.

I'd try cleaning up the pins and if possible even the female pins in the harness side. Then give it a try. You might as well open the case of the FICM and have a look inside to see if there is anything burned up.

Luckily LB7 FICM's aren't that difficult to find and they aren't as expensive as the LLY ones. So you might be better off replacing it rather then having it repaired if it's burned or you can't get it working properly.

But do make sure you inspect the harness connector pins carefully so you don't cause issues with the replacement or your current one if you get it working
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Would it be possible to back probe the harness connectors to see what voltage the truck is outputting? The transparent issue is when the truck is driven to operating temperature and then put into park, the truck seems to start to have an inconsistent miss. For a while I thought it was the EGR activating but it does it with the EGR motor unplugged and the MAF at 42 gr/s so I know that it is something else.

Can the LB7 FICMs be used on the LLYs? From what I have read their outputs are completely different.
 
2004LB7

2004LB7

Well-known member
Dec 15, 2010
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Have you been following the LLY FICM thread? That should give you enough information to be able to measure the voltage, resistance, etc. it's a long read but if you can't make heads or tails from ot you're probably better off taking it to a shop or having someone else look at it
 
T

Trgglynn

Member
Jan 5, 2024
63
4
8
Portland, OR
2004LB7 said:
Have you been following the LLY FICM thread? That should give you enough information to be able to measure the voltage, resistance, etc. it's a long read but if you can't make heads or tails from ot you're probably better off taking it to a shop or having someone else look at it
Click to expand...
Very helpful. It looks like I need a back probe kit. Do you happen to have a pin out for the ECM feeding to the FICM? Looks like I need to test for 5v on control and 48v coming out of the unit? Probably should also test for resistance across the harness. Hopefully I am headed the right way in that.

As far as the LLY FICM thread, that is a lot of good info. Admittedly it all goes over my head quite a bit, I’m not to sure if I could interpret a oscilloscope reading.
 
2004LB7

2004LB7

Well-known member
Dec 15, 2010
6,969
2,137
113
Norcal
Trgglynn said:
I did find someone I know with a LB7 FICM module. Is it feasible to work with a LLY? I’ve seen varying conclusions of yes and no. I do know it will try to drive the injectors with a lot of voltage, which concerns me.
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As Brad said. They use the same pinouts but speak different languages so they are not interchangeable
 
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