LS3 swap, electrical help

WP29P4A

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I'm working on the electrical on the rock crawler Jeep again. This time I'm installing a new gauge cluster and I'm trying to find a connection diagram for the computer on a new LS3 engine. I need to find a connection for the tach.
 

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I'm working on the electrical on the rock crawler Jeep again. This time I'm installing a new gauge cluster and I'm trying to find a connection diagram for the computer on a new LS3 engine. I need to find a connection for the tach.
Just a wild guess... Black connector Pin #48, add a 1K resistor, and an adjustment to the tune to activate the signal

Lots of threads about this on Camaro forums
https://www.camaro5.com/forums/showthread.php?t=494026
 

Bextreme04

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I'm working on the electrical on the rock crawler Jeep again. This time I'm installing a new gauge cluster and I'm trying to find a connection diagram for the computer on a new LS3 engine. I need to find a connection for the tach.
What do you mean "new" ls3? What ECU are you running? What is your tuning program? Are you referring to a Gen IV LS from the ~2008-2014's... or an actual LS3?

I would assume maybe you have an E67 ECU?

If so, these guys say to connect pin C1-25 and C1-24 and then that splice can be connected over to the tach. C1-24 is a pull up resistor circuit.

https://forum.efilive.com/showthread.php?20663-E67-Tach-signal-pinout/page2
 

WP29P4A

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Getting access to the computer is very difficult. I'm hoping to find the wire that "was" connected to the old cluster in the dash. Any idea what it "looks" like when you connect a meter to it? Low voltage with pulse?

This Jeep with the LS3 conversion, two computers and no wiring diagram, no history of what the conversion team did to the wiring, I'm REALLY having to earn my money on this project/ LOL
 

WP29P4A

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What do you mean "new" ls3? What ECU are you running? What is your tuning program? Are you referring to a Gen IV LS from the ~2008-2014's... or an actual LS3?

I would assume maybe you have an E67 ECU?

If so, these guys say to connect pin C1-25 and C1-24 and then that splice can be connected over to the tach. C1-24 is a pull up resistor circuit.

https://forum.efilive.com/showthread.php?20663-E67-Tach-signal-pinout/page2
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I don't have the answers to any of those questions, it says LS3 on the engine, I cant get to the controller without removing lots of other parts to see what it is. I'm not worried about the tuning program because it's was done by the conversion company and it runs more than fine, not my job. I'm just converting from the stock gauge cluster to auto meter gauges and replacing the accessory switching again.
 
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WP29P4A

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By new, I mean brand new crate engine with transmission and computer/controller. I have NO paperwork, no written or printed information on this installation. The only help I have is my digital meter, 40 + years of working on stuff and common sense.

I really appreciate the links to the information you guys posted, I hoping to wrap it up today and just need to find the speedometer, tach and fuel wires. Everything else is done and tested.
 

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oh man... You need a picture of the ECM. What trans did they put in? Was it one of the "connect and cruise" kits from GM?
 

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What gauge cluster are you using?
 

WP29P4A

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oh man... You need a picture of the ECM. What trans did they put in? Was it one of the "connect and cruise" kits from GM?
You have GREAT questions and I wish I had answers, going to go over now and going to question the owner to see if he has anything helpful. Bringing my lap top with so I can look at the links you guys sent and check back once I get some answers.

Will the ECM have markings on the outside of the case or do I have to open it?
 

WP29P4A

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What gauge cluster are you using?
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It's my first time doing a gauge cluster, I could do better on the wiring neatness with a little practice.
 

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The tach and speedometer worked before I started, but were not accurate which is the reason for the gauge conversion.

I will check back when I am on site, hopefully with some answers.
 

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Who did the conversion? Bruiser? Motech? AEV? I'd give them a call to see if they have your answer.

If not @Bextreme04 is right, you need to know what type of ECM it has.
 

Bextreme04

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The tach and speedometer worked before I started, but were not accurate which is the reason for the gauge conversion.

I will check back when I am on site, hopefully with some answers.
Oh no. The gauge conversion will not fix them being inaccurate. You need to get into the tune and correct it there. EFILive or HP tuners would let you get into the tune and adjust the parameters to read correctly with whatever gauge you are using. It is unlikely that these new gauges will just suddenly read accurately without more adjustments in the tune. The RPM is coming off the crank/cam signal and is interpreted in the ECM, adjusted according to the parameters in the tune, and then output as whatever signal you spec in the tune.

The speedometer signal is similar, but comes from the VSS on the transfer case and is then adjusted by factors in the tune to get the correct reading at the speedometer.
 

WP29P4A

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Who did the conversion? Bruiser? Motech? AEV? I'd give them a call to see if they have your answer.

If not @Bextreme04 is right, you need to know what type of ECM it has.
A place in So. Cal did the conversion. If they were real humans I would not be cleaning up their mess, and no they are no help, or I would not be here asking you guys. Very thankful for your input. I got the speedometer worked out and I'm just about ready to test it.

The part/model # on the ECM is LS3761480.

The gauge manufacture says connect straight from VSS signal to speedometer.
 

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