For all you guys out there that have replaced the stock PCM with an aftermarket system.

Did you leave the stock PCM in place and piggyback the harness?

If not, what did you do to run the tach, speedometer, etc?

Thanks,

--Sean

 

When I installed the MoTeC M48Pro, I piggybacked it on the stock harness where possible, and kept the stock PCM for VSS, IAC (MoTeC will only drive PWM, not stepper type IAC), AIR, EGR and EEC. Where I got into problems was with the IAT and CLT temp sensors. Essentially, when you have a pure resistance device (no +5V bias feed like you have on TPS, MAP, etc.) you need a parallel sensor to feed two independant computers. Stock PCM still feeds the stock tach, but I also feed a 5" tach from the MoTeC.

 

Interesting.. Did you remove any of the stock harness.. Get rid of things you didn't need anymore?

--Sean

 

I have a ton of unused "connectors" from the stock harness.... I run speed-density, so no MAF, I run a MoTeC IEX 8-channel ignition driver with LS1 coils, so no coil or ICM connectors, the AIR, cruise control and A/C have since disappeared, so all those connectors are hanging loose. No knock sensor, with the solid roller cam, to that connector is hanging there. It is programmed to run open loop, but the O2 sensors are still plugged in, and I can read them via a ScanMaster, for entertainment. The EGR and EEC are about to disappear... so those harness connectors will be hanging loose.

I think I could make a major weight reduction in the car if I just pulled out all the unused wiring, but that seems like a very "final" step.... e.g. it will never be a street car again.