No tacho signal from ECM?

[jet231]

Hi guys,

I have an LS1-b ecu with the red and blue connectors and am trying to get my autometer tacho working with it. Motor is in a new chassis, so there is no existing wiring. Basically from what I have read, I should have a 5v square signal coming from pin 10 on the red connector. Also read that the autometer tacho needs a 12v square signal and to use a pullup circuit etc..

Basically, I have tried using a few different sized resistors and the tacho still isn't working. After using a scope, I am finding that I am not getting a square signal out of the ECU. At most I get around 100mv messy signal with a few minor spikes here and there.

Can anyone confirm that it should have at least a 5v square signal from pin 10? Wire colour is brown..
ECU info follows:

Serial 1DG1020S0062
Hardware 16220610
Operating System 01290005
Calibration N/A
BCC MOD5
Operating System 01290005
Engine Calibration 92158594
Engine Diagnostics 92158604
Transmission Calibration 92158614
Transmission Diagnostics 92158624
Fuel System 92158634
System 92158644
Speedometer 92158654

Thanks

[400ss]

Hi, i have the same problem here.. working on a XJ cherokee with an LS6, using GTO 04 base tune,, everything is working, exept tacho.. i keep the stock cherokee gages, using novak cam crank signal converter to feed the jeep ECM to control the gage.. but my RPM signal from the ECM is not working i even tried the resistors too, and i have a code about engine output speed signal circuit something like that but the wire does is wired correctly, it came directly from the PCM RPM pin

[jet231]

Can anybody confirm? I'm not running any signal converters. Just a direct feed from pin 10 to tach. No error messages either