no tach signal out of ls3 ecm, need magic man!
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hi, new guy here. just installed new crate motor, trans, and harness (from gm) in a 69 camaro, starts and runs, no codes, can read cam/crank sensor and rpm with scan tool, but no signal from bulkhead connector for tach or trans. it says its a low voltage 2 pulse/rev squre wave. with a meter, i have no wave form at all from either the bulkhead, or the ecm pin no (25 blue connector) what am i not getting? i think there will be a prize for the right answer. thanks for any help. hb
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I had the same problem (posted an earlier thread) when trying to interface the Dakota Digital VHX with the ECU in my 67 Camaro. All we did to fix it was change the tach setting to "crank" in the tune and it worked fine. No need for a pull-up circuit. That was with the DD anyway - not sure if it works for other tachs.
regards
regards
#7
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LS3R8 suggestion will also work with an Autometer tach.
Jon
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Jon
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#8
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hi guys, i guess that i got a little technical with the whole problem, i wanted to see a signal out of the pcm, we tried all of our fancy test equipment to no avail. set tach to four cyl, installed resistor, and it worked. amazing what you can do to out-think yourself. thanks to all of you that persuaded me to follow the instructions. happy motoring. hb
#9
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Ha! Dude i chased a small wiring problem down for days and days I was CERTAIN it was tune related as the VATS patch was not sticking more than once per start up. Meaning the thing started and ran fine until i shut her down then it would only start on a handful of cylinders so I would flash VATS back off and it would run great again. So after teching myself and everyone else on the boards nuckin futz I finally poured over my wiring and voila found that one of the power feeds was hooked to bat instead of ign. Wired it up correctly and voila problem solved
Moral of the story? One never knows..... until you know![EEK !!](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_eek2.gif)
Glad you got it sorted.
Moral of the story? One never knows..... until you know
![EEK !!](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_eek2.gif)
Glad you got it sorted.
#10
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I used this thread to get the tach to work:
http://www.hptuners.com/forum/showth...ach-(autometer)
Does anyone know f something similar has to be done in order to make the speedo work? I've tried everything and still have not gotten it to work. Thanks,
Rob
http://www.hptuners.com/forum/showth...ach-(autometer)
Does anyone know f something similar has to be done in order to make the speedo work? I've tried everything and still have not gotten it to work. Thanks,
Rob
#13
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I used this thread to get the tach to work:
http://www.hptuners.com/forum/showth...ach-(autometer)
Does anyone know f something similar has to be done in order to make the speedo work? I've tried everything and still have not gotten it to work. Thanks,
Rob
http://www.hptuners.com/forum/showth...ach-(autometer)
Does anyone know f something similar has to be done in order to make the speedo work? I've tried everything and still have not gotten it to work. Thanks,
Rob
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#17
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![](http://www.lt1swap.com/pictures/tach_circuit_fix.jpg)
To make the speedo work, I used this circuit coming off C1 (Blue) pin 39 and set the speedo output to "Serial"
![](http://i152.photobucket.com/albums/s162/fieroguru/Wiring/49f82fd1-778e-48a2-9855-6a2b2227b4e0.gif)
Last edited by fieroguru; 12-13-2013 at 06:50 PM.
#18
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Here's the answer to the Speedo problem:
Chris - I downloaded the new version of HPTuners and made the changes - you da man!!! The speedo now works correctly!!! Thanks again,
Rob
please post up your tune so I can take a look or email me chris at hptuners.com
Hi Rob,
Please download the latest 2.24.469 or later.
I have added a new parameter to the speedo section called “Speed Output Type”, try setting this to “VehSerial”.
This parameter is used by the ECM hardware driver to initialize the output correctly.
Please let me know if it works.
Chris…
Hi Rob,
Please download the latest 2.24.469 or later.
I have added a new parameter to the speedo section called “Speed Output Type”, try setting this to “VehSerial”.
This parameter is used by the ECM hardware driver to initialize the output correctly.
Please let me know if it works.
Chris…
Rob