2005 L33 Tach Output?
03-30-2012, 08:55 AM
#1
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2005 L33 Tach Output? Have a L33 from 2005 Silverado and the computer reads as a 2005 GMC Sierra.
The tach is an Autometer ATM-3698
I have installed 2 different computers with the same tune and the tach does not work on either of them.
Here is what i have done..
Computer was programmed by a company that seems to do many (no need to call out names). Installed a 1K pull up resistor to 12V as instructed by them, nothing on the tach. Discussed the issue in detail with the programmer and autometer. Autometers first response is to purchase a tach adapter, they have lots of issues with LS motors and tachs. The programmer worked with me and sold me another computer with the same tune. Plugged it in and no tach. Tested the tach on a function generator with a 5V square wave signal as instructed by autometer, tach worked on function generator. Autometer then told me to install a 10K pull up resistor to 5V reference wire, still no tach.
I got HP Tuners to be able to program the computer myself and the only settings for tach output on the software is high resolution and low resolution, I have left them set at 6 (how it came), tried 3, and also tried 8 for both setting and got nothng on the tach.
I have tried every different cylinder pulse setting possible on the tach, the tach just always reads zero..
Tach wire is coming from pin 10 on the green connector. 5V reference wire I have installed in pin 7 on blue connector and tests correctly.
Hooked an oscilloscope on the tach wire with the 10K pull up resistor to 5V reference and get no signal.
How much current can the tach outpout on the computer handle before its damaged? 1K on 12V is around 20 miliamps and 10K on 5V is bout .5 milliamps. Could the output be damaged on both computers because of the 20ish milliamps.
What kind of readings should i get with a miltimeter on the tach output if its functioning properly?
Any suggestions??
The tach is an Autometer ATM-3698
I have installed 2 different computers with the same tune and the tach does not work on either of them.
Here is what i have done..
Computer was programmed by a company that seems to do many (no need to call out names). Installed a 1K pull up resistor to 12V as instructed by them, nothing on the tach. Discussed the issue in detail with the programmer and autometer. Autometers first response is to purchase a tach adapter, they have lots of issues with LS motors and tachs. The programmer worked with me and sold me another computer with the same tune. Plugged it in and no tach. Tested the tach on a function generator with a 5V square wave signal as instructed by autometer, tach worked on function generator. Autometer then told me to install a 10K pull up resistor to 5V reference wire, still no tach.
I got HP Tuners to be able to program the computer myself and the only settings for tach output on the software is high resolution and low resolution, I have left them set at 6 (how it came), tried 3, and also tried 8 for both setting and got nothng on the tach.
I have tried every different cylinder pulse setting possible on the tach, the tach just always reads zero..
Tach wire is coming from pin 10 on the green connector. 5V reference wire I have installed in pin 7 on blue connector and tests correctly.
Hooked an oscilloscope on the tach wire with the 10K pull up resistor to 5V reference and get no signal.
How much current can the tach outpout on the computer handle before its damaged? 1K on 12V is around 20 miliamps and 10K on 5V is bout .5 milliamps. Could the output be damaged on both computers because of the 20ish milliamps.
What kind of readings should i get with a miltimeter on the tach output if its functioning properly?
Any suggestions??
03-30-2012, 10:00 AM
#2
This seems to be a common problem on 2001 and newer engine computers. There was a thread that had a diagram but this is all I could find in a quick search: https://ls1tech.com/forums/conversio...-tach-yes.html
03-30-2012, 05:05 PM
#3
If you are sure the tach works, install a 600-800 ohm resistor, one side to the tach output, the other to +12V.
I have done it a couple time witn no issue.
10K with 5V is not going to work.
I have done it a couple time witn no issue.
10K with 5V is not going to work.
03-30-2012, 07:50 PM
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I have already tried a 1K resistor to 12 volts and a 680 ohm resistor to 12 volts and nothing with either.
What kind of signal should i read on the tach wire with a multimeter or oscilloscope?
Either the computer output is dead or the tune is not taking the tach signal? I have tried 2 different computers so i don't think it is the computer. I have also tried a different tach.
What kind of signal should i read on the tach wire with a multimeter or oscilloscope?
Either the computer output is dead or the tune is not taking the tach signal? I have tried 2 different computers so i don't think it is the computer. I have also tried a different tach.
