dhall243

Hey guys and gals, Im going to pick up a 99 Formula Firebird later this evening, car has a tick in the ls1 so I'm going to swap it with an LQ4. Ive got a complete Holley EFI system.

My question is this, if i Remove the factory PCM what functions will I lose, and will it affect the T56 in anyway? Is the fbody gauge cluster like the silverado cluster and hold the miles on the cluster itself or does it get the info from the PCM?

Holley has inputs and outputs so I can run the Speed Sensor threw it and back out to the cluster.

Mike454SS

iTrader: (4)

The T56 reverse lockout (and if you care, skip shift) is run by the PCM. Maybe the Holley setup can control that too? You can get into reverse when it's locked out, but it's annoying compared to having it work right.

MontecarloDrag

iTrader: (3)

You will lose some gauges. You can make the voltmeter and oil pressure work with the holley, but the others are Class-2 and need the PCM to command them.
It means no tach, no coolant temp, no speedo and no fuel gage unless you install aftermarket gages and senders. No OBD-II diagnostics too, if you need to pass emissions it will be a problem.

The mileage is stored in the cluster itself and nowhere else. AFAIK the Holley EFI doesn't have a 4000 PPM speedo output, so you will lose speedo and odometer too, unless you install a buffer or DRAC module to translate the Vss AC signal to 4000 PPM for the cluster.

soundengineer

iTrader: (16)

The Holley HP does not have a speedo out
But the Dominator does...

And You are better with an aftermatket tach anyways because the f-body tach is slow because its using serial data fron the ecu instead of directly driven by pulses

Skip shift doesn't need anything...
Most people want to eliminate it anyways...
The reverse lockout can be controlled with 12v and a relay.. just send voltage to it and it eliminates the reverse lockout..
No need to try to command it from the Holley and waste a pin and an output.

moehorsepower

iTrader: (3)

Yup When mine was an auto I had a switch for the lock up, now its a Stick, I just used the same switch and did the 12volt hook up..Works fine.