eljorg89

I have a Gen IV 5.3L with a e40 ecm that was installed into a Jeep TJ. All is working except the tach. I have a tach emulator from Novak (the pull resistor is insalled)and the tach is still not reading correctly. I have used an oscilliscope to see the signal from the 48 pin (white - tach signal) from the ecm and it is not a square wave. more like a sine wave at low voltage. higher voltage with the pull up resister, but still doesn't work.

In researching this issue, I have seen a number of posts about the e38 ecm that needed to have the ecm programmed to crank and not freqency. Is this the same with the e40 ecm? (perhaps, the ecm was not set up correctly when I had it reprogrammed.)

Any help with figuring out how to get a square wave from the ecm would be appreciated.

Thanks,
Erik