sunchaser73

I could use some help with PCM pinouts and PIDs. Where do you obtain the information that gives you a PID for a specific pin # ??

For example, I have the learned the following from reading the "Wideband" sticky (great info...):
C1 connector, Pin # 55 is for EGR, PID.2811
C2 connector, Pin # 14 is for AC pressure, PID.7101

How do you get this information?? Is there a standard list for LS-1 PCMs that correlate PIDs to each pin? There are many unused pins (on the C5) that may have a use/function on other LS1-based vehicles.

Help of any kind would be greatly appreciated. Thanks.

sunchaser73

bump...
Anyone?...thanks.

chevy406

You need to find the wiring diagram for the specific vehicle you are working on. 97-98 C5s will be different from 99 and up C5s, F-body will have differences (drive by cable). Check on LS1Tech or get a 1 month subscription to Alldata. A simple Google search will probably get you an answer. If you PM me your email address I can attach an ECM wiring diagram for a '99 Corvette.

sunchaser73

I have both the wiring diagrams and an AllData subscription. Neither of them tell you what the unused pins are for. They are used on other LS1 engines like the Camaro and Firebird, so there mist be a corresponding function and PID for the PCM-side pin...that's what I'm looking for....

chevy406

Unused pins are just that - unused... The ECM is only programmed to read data from the pins that it needs.

Maybe this will help. For my 69 Nova LSX conversion, I bought a '99 C5 ECM and engine wiring harness. Since I am running a cable throttle body, I converted the wiring harness to be similar to a 2002 F-body harness. Basically I added throttle position and IAC pigtails and plugged them into the C1 and C2 connectors according to the F-body wiring diagram. I also took out circuits that my installation didn't need (emissions, transmission, rear O2, etc). Then, using HP Tuner, I re-flashed the operating system in my C5 ECM using a stock tune from a 2002 F-body. Now my ECM recognized the TPS and IAC even though those pins weren't used when it had the Corvette operating system.

So I don't think you will be able to communicate with the ECM through pins that aren't being used, unless the ECM is programmed to read data from that pin.

sunchaser73

chevy406 - thanks for the info. What you're saying is pretty much what I am getting at: are there functions/PIDs that the 99 C5 PCM is capable of reading (ie, programmed for) but "do nothing" because the sensors aren't there?

Or to put it another way, I want to add two more PIDs using dedicated pinouts. I've read about how alot of guys use the AC pressure pinout and put a switch in so that they can log AFR on the dno and then switch back to AC pressure on the roads...trying to avoid that, though...doesn't seem like I can pull that off...guess I'll just have to add a switch on the AC pressure wiring and hook up everything I need for the data-logging I want to accomplish.

Again...thanks for your reply...very helpful!