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Splitting crank trigger signal

Practical Motorsport Wiring - Club Level

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I have a 2006 Corvette Z06, and I am getting ready to make the change to a Haltech Elite 2500 from the factory ECU. I know to do this you need to piggyback the factory ECU for running the factory instrument cluster, and ABS while using the Haltech to run the engine itself. Currently there is very little information about this available through searches, and the people who normally do this tend to keep the information fairly secret, as they make their livings off of it. Which is fine, and completely understandable. I'm sure I can figure the bulk of it out, and add sensors to keep systems mostly isolated.

Normally, in most electrical systems, we wouldn't mix voltage from 2 different systems as it can cause some major issues. However, the crank trigger signal is the one thing I can't seem to figure out how to get to both systems in an isolated manner. Would this matter? Do we need to keep them isolated since they're both technically from the same 12V power source and just dropping sensor supply down to 5V on different sets of diodes?

I can easily add a second coolant temp sensor, and another oil pressure sensor that will be used just for the Haltech system. And I shouldn't need to split the home signal.

Any help or ideas would be greatly appreciated. Thanks!

Hello Ken

When doing a piggyback you are best to leave as much as possible factory. So try to share the sensors retaining the factory power supplies. Pullups in your ecu should be turned off. Temp inputs do not have the option to have the pullup turned off as far as I'm aware so will either need a second set of sensors or be wired to AN volt inputs and use a custom cal.

Just use the signal from the crank sensor. Do not try to supply voltage from your Haltech, let the OEM ECU power the sensor. The Haltech should have a high-impedance input so it should not affect the signal the OEM ECU sees.

Thank you! I’d planned on adding new coolant temp, and oil pressure sensors for use with the Haltech anyways, to isolate the 2 ECUs as much as possible. And since the Cam sensor won’t be needed in the factory ECU anymore, I can remove the factory connection to it and use that only for the Haltech, and the same would apply to the knock sensors. Thanks again, this has been massively helpful!

hi Ken,

Its a bit more of an academic project the CAN stream to the dash can be reverse engineered using something like a 'CAN sniffer' to generate a .dbc file that will allow the Haltec to transmit ECU data to the dash display however If your OEM ECU has some body controller or PDM functions then this could get a little harder but being 2006 I wouldn't expect it to be so sophisticated.

Scotty88, this is something I have considered. Ultimately I haven’t done enough research into the process to see if it’s viable for me at the moment, but it is something I would love to do. I know the car has a body control module that deals with things like the ABS system and the electronic door/lock actuation, but whether or not it’s on a shared CAN network with the ECM is not something I could say with any certainty.

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