Problem with tachometer and hp Tune tach settings

To any body with experience with retro fit old school with new school and tuning the tachometer settings on hp tuners. This is what my problem is, and what I'm doing. I'm using the original 4 pulse tachometer that ran off of the distributor on the 1978 350 corvette. I'm using a 06 GTO LS2 and 4l65e platform dropped into the old 78 corvette. When in HP tuner with the setting on crank and res 3/3 high/low (24x crank) should create a 4 pulse signal as far as I'm told, but with all that set with the pull up and 1k resistor in place the E40 will not ground it out and create the pulses. Now with the setting in HP tuner set on frequency it at least moves the tachometer and grounds, but is about (analog) 2 pulses off and keeping in mind the tachometer is calibrated. What is your thoughts on this am I missing something, or is the computer bad? I have check all connections multiple time and the plug on E40 found everything in order.

I'm having this exact same problem, except I am looking at a 67 Camaro with a 06 GTO M6 ECM. Crank seems to do nothing on any setting. With frequency, the tach responds but behaves a little bit bizarrely.

Has anyone successfully used an E40 ECM with a stock 4ppr tach?

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Originally Posted by Shark Racer

I'm having this exact same problem, except I am looking at a 67 Camaro with a 06 GTO M6 ECM. Crank seems to do nothing on any setting. With frequency, the tach responds but behaves a little bit bizarrely.

Has anyone successfully used an E40 ECM with a stock 4ppr tach?

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So, I kind of got this working.

I bought a spare SunPro tach. Verified that it worked fine on a known good car, and then hooked it up to the Camaro/E40. With Frequency / 2/2 the Sunpro read correctly when set to 4 cyl setting(and using a 1K pull up resistor). So, I knew that the circuit was fine. What was interesting was when we set the tach to 6 cyl, it mapped pretty closely to what the 67 Camaro tach was showing.

We tried setting the GTO ECM to Frequency 3/3, but this did not get us where we wanted. Can anyone explain the frequency setting?

Fortunately, we had a Dakota Digital converter box and set it up for 4cyl input, 6 cyl gauge and now the tach is working fairly well. A bit slow and off by ~100 RPM, but scaling correctly. Serviceable.

I'd really like to know how the frequency setting works, though.

www.google.com

Enter:

site:hptuners.com tach setting

http://www.hptuners.com/forum/showth...ch-(autometer)

http://www.hptuners.com/forum/showth...der-tachometer

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Originally Posted by mecanicman

www.google.com

Enter:

site:hptuners.com tach setting

http://www.hptuners.com/forum/showth...ch-(autometer)

http://www.hptuners.com/forum/showth...der-tachometer

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Thank you - I read both of those already prior to posting this and searched the forum to drag up this thread. :)

The first thread:

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The two options for tach output are frequency and crank. I do not know what frequency is, I tried it, it did not work for me, I got “crank” to work and I understand “crank” so I do not care about frequency.

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The second thread has someone asking what the difference is between serial, frequency and crank with no answer.

The E40 ECM seems to work opposite of the E38. I do not have an oscilloscope (yet), but setting tach output to crank made every tach I threw at it show no output. Frequency 2/2 (default for an E40, at least in the Corvette and GTO cals I looked at) seemed to be the only one that worked and gave a 4 cyl output. I assumed it was PPR, but that did not result in an expected outcome when I set it to 3/3 (the 67 Camaro tach should have shown an 800 RPM idle, but it was somewhere below that).

Crank made some level of sense to me, but as said, it did not seem functional when we tested.

Has anyone figured this out for the E40's?

I'm putting an LS2 into an E36 and the tach won't respond to frequency changes. The tach always reads about 1/2 the actual RPM. A dozen high/low frequency changes did nothing.

I tried the 'crank' setting instead of 'frequency' but then the tach needle just doesn't move (even with a pull up resistor). The voltage at the tach signal line just sits at ~14V.

I never got my E67 tach output to work with my Autometer tach... so I bought a Dakota Digital STA-1000 to read RPM from the OBD-II port and generate a signal that my tach likes. This might work for you -- https://www.dakotadigital.com/pdf/STA-1000.pdf

Hello all. I have a similar problem and was going to start my own thread, but found this one.

A family member has a 1937 Chevy with a 2005 Envoy/Trailblazer 5.3 V8 and 4L60 trans combo for the drive train. The ECM is an E40.

I’m working out some bugs with this vehicle and I’m almost done with my list. The last electrical thing on the list is getting the Tachometer to work. The tach (engine speed) wire is leaving ECM plug C1 pin 48 and goes to a Dakota Digital VHX box which is essentially a tachometer converter among many other things.

Facts:
-I can read/see RPM in VCS scanner via the OBD/DLC.
-The tachometer in the instrument cluster does not indicate anything regardless of engine speed.
-I have the Dakota Digital box set correctly as 4 cylinder engine and 5v signal (12v is used on coils, manual says to use 5v for ECMs)
-The needle moves when tested. I can perform a test and sweep the needle
-The CURRENT tach output setting as read in VCM editor is: <type> CRANK, Resolution High 3, Resolution Low 3. A STOCK tune from a 2005 Enjoy/Trailblazer 5.3 with E40 ECM tach output setting is different and is: <type> FREQUENCY, Resolution High 2, Resolution Low 2.

I have read that LS engines need a pull up resistor on the ECM tach wire. Essentially this is a 1k ohm 0.25 watt resistor tapped into a 12v lead and spliced into the tach/engine speed wire. I don’t think is required as I have another vehicle with the same setup (E40 ECM with Dakota Digital tach adapter) that works without it. I’m leaning toward the tach output settings in the tune being the cause (like mentioned above). I don’t know the reason why they were changed from stock.

Anybody have any insights or input on this? Thanks!

I think I would try changing the settings to match the one you know works.