Hey Guys,
Back for more help. So---I've got the original harness and PCM off of the 97 Z28 in my 39 Chevy chassis. Using info from Shbox.com, I hooked up everything that was listed as needed. Problem is, when I got the harness, someone had cut it off at the firewall, so no DCL. Can someone tell me what wires I have to connect to get the engine to start and run? Not concerned with how it runs right now. I have a 95 PCM OBD1, coming. I have an Aeromotive in-tank fuel pump and fuel reg that I will control. Need to know what else needs to be hooked up to start and run.

Thanks

shbox.com has the PCM wire diagrams, 4th Gen LT1 F-body Tech Articles

to start it up you need.... +12 battery on 2 pins, +12 ignition on 2 pins, fuel enabled on 1 pin and fuel pump relay pick to relay from the PCM. Not inside the car, but still needed are two ground spliced black wires to stud on block above starter and two tan ground wires on stud in front of left head near the ICM.

In the F-body these lines all come/go from to passenger compartment. Do not know how you wired up the 39 chassis. I doubt you have a theft deterrent module that generates the square wave "fuel enabled signal (VATS)" to PCM . So you can disable that in the tune. The others may or may not be used depending how you wired things up (EG where you put the fuse box for +12 batt and 12 v ign to PCM. Same w/fuel pump relay, it's under dash in F-body, yours may be elsewhere. Depending on what you are using for tach and speedo gauges you may be feeding a signal converter box first

There are other lines, not critical to start, but needed for correct operation.

The ALDL serial data line and connector is required for tuning and scanning
Malfunction Indicator lamp (SES) light
Park/neutral to control idle in A4 setups.
Brake switch to kill the TC lockup in A4
Traction control if used
Performance mode switch and indicator if used
Speedometer and tachometer lines
AC request if you are installing AC

Thanks for the reply. I posted some pics of what I'm working with. Body's not on the chassis yet, so I have easy access to all wiring connections. As you can see, the harness was cut right at the outer firewall. I may have to get another harness if I can't sort this one out.

QUOTE=bobdec]
fuel enabled on 1 pin and fuel pump relay pick to relay from the PCM
[/QUOTE]
I will control the fuel pump with a keyless ignition system. Is this OK or does the PCM require fuel pump feedback?

QUOTE=bobdec]
Not inside the car, but still needed are two ground spliced black wires to stud on block above starter and two tan ground wires on stud in front of left head near the ICM.
[/QUOTE]
I only saw one large ground wire to block above starter, which I secured to the block. I secured the wires to the head at the ICM.

QUOTE=bobdec]
I doubt you have a theft deterrent module that generates the square wave "fuel enabled signal (VATS)" to PCM . So you can disable that in the tune. [/QUOTE]
I’m installing a Viper theft deterrent system along with GPS.

QUOTE=bobdec]
The others may or may not be used depending how you wired things up (EG where you put the fuse box for +12 batt and 12 v ign to PCM [/QUOTE]
Not sure where to wire a fuse box into the harness. Need some advice there.

QUOTE=bobdec]
The ALDL serial data line and connector is required for tuning and scanning
Malfunction Indicator lamp (SES) light
Park/neutral to control idle in A4 setups.
Brake switch to kill the TC lockup in A4
Traction control if used
Performance mode switch and indicator if used
Speedometer and tachometer lines
AC request if you are installing AC
[/QUOTE]
These are things that will be addressed when I get to installing the body on the chassis. Again, I don't see how I can get the done without purchasing another harness. If I get another harness, should I get one for a 95 engine (OBD1)? since the is the PCM that I have coming.

A/C is Vintage Air with digital controls.

Really appreciate the help.

Headed to the shop for day 2 with the wiring

Anybody know the color of the wires that require constant 12V and switched 12V? PO cut the datalink off of the harness before I got it.

Thanks

pink is ign switched power and orange is constant where the body harness connects the engine harness

but you should really get a wiring diagram

Sorry I was answering for the PCM only (power train control) harness wires.. looks like your pic is the total body harness. Things like ignition to starter, horn, HVAC blower motors, lights, oil, fuel temp gauges and lots more. What you are doing will require a custom body harness. Eg the starter solenoid circuit would have to be from whatever ignition switch you have, to whatever neutral safety switch you use, to the starter solenoid. That has to be repeated for everything like horn, head lights, turn signals, brake lights, HVAC blowers, AC, etc.. almost all those runs will be a custom routing in this situation.

To ans some questions.
1- The fuel pump does not provide any feedback to the PCM, since you will be activating the pump outside the PCM then that circuit is not used. BUT the PCM kills the pump if engine stops (AKA: an accident) as a safety precaution. Tieng it directly to key keeps it running in that situation, older cars used an oil pressure switch as a safety cut off.
2- The two black ground wires to PCM are spliced together in the harness there is only 1 round terminal black wire on that stud.
3- Even though you are activating the FP externally, the PCM looks for a square wave on 'Fuel Enable line" , if not there the injectors will not pick. This injector disable can be tuned out (VAT's disabled) or your Viper would have to supply the signal. Not knowing the system I can't answer if it's supplied from the Viper. E-Bay sells VAT's bypass systems that generate a signal that can be sent to the PCM, you're going to need a tune any way so just tune it out.
4- You will need one or possible two fuse boxes somewhere for the 20-30 fuses (depending on how you design power distribution) needed for the electrical system. Placement should be where it will remain dry w/convenient access with shortest wire runs. Under the hood is usually the easiest to wire and access.

Yea, I know. I followed the diagrams on Shbox.com and they really helped me out. Thanks for the info.


Thanks again for the very informative post. Most of that harness will not be used. I am also installing an electronic shifting mechanism (push button) so interior wiring will be extensive. The part about fuel pump cutoff I'm going to have to look at. My Aeromotive pump may have provisions for that built in, not sure.

Just a follow up.. I want to clarify wiring , The PCM harness does not go through the firewall. It has connectors to the main body harness that goes through the firewall. As an example look at this pic of harness ref shbox.com 1995 Z28 A4 Engine Harness . The two +12 batt orange lines to PCM are spliced together in the engine harness and go to connector C210 pin C and the two +12 ignition on pink wires are spliced together in the engine harness and go to conn C230 pin G. Once the plug into the body harness splices in that harness then spider the circuits to many other points and to the instrument panel fuse box. What you have to do is either 1 - custom wire the lines I mentioned to the engine harness by either splicing into it or purchasing applicable connectors to mate with the engine harness.. OR 2 - wire the lines directly to the PCM pins and bypass the engine harness. Part of the fun in building/designing your own car is the choice is yours. Hope this helps , not adds confusion..

Hey Bob,
Thanks again. I not sure I completely comprehend what your saying. Here is a picture of my harness as I got it from the PO. He said that he cut it off where it goes thru the firewall, the part that I have circled in red.

So--that part that I have circled is actually C210, C220 AND C230 in the pic from shbox.com, right? Are the spider circuits you speak of, inside the vehicle? When I purchase my vehicle wiring, from painless or some other supplier, won't those circuits be in the new harness? Maybe I'm not understanding completely.

Thanks

I screwed up.. I should delete my previous post it is incorrect I missed seeing C210,C220 and C230 are inside the car when I looked it up. That grommet in shobox's link is called P110 in wiring diagrams and it goes through the firewall. I completely missed that.. The Painless engine harness should come w/diagrams to get all that working. Here's a bigger pic http://shbox.com/1/harness6.jpg . Your pic in post #5 looks like it has more wires than those 3 connectors have.

There are definitely more wires on my harness. Mine harness is from a 96 Firebird TA, so not sure if it is different than what is shown on shbox.com. Still working through it. Do you know where the PCM gets it's power from? Also, I understand that I have to tune the VATS out, but if the purpose of the VATS is to keep it from starting unless the key fob is present then how do I get the engine started to tune the VATS out?

Thanks

No need to start engine to tune it. Just need key on. OR-- If you put +12 batt on pins B15 and B31, +12 volts ( simulating ignition) on pins B30 and D03 , Battery ground on pins A02, C32, A18 & D1 the PCM will be running and operational . You can then connect the serial data line to Pin D30 via the ALDL cable and program it scan it etc using a scan tool or PC w/software.. You s/b able to connect +12 and ground directly to the PCM harness using these as a guide.. ref shbox.com 4th Gen LT1 F-body Tech Articles .

ALSO this a great link.. you are interested in C210, C220 and C230 pages they give the colors and should match you cable cut http://shbox.com/1/harness_connector_faces.htm

By the way the older F-body 4th gen VATs is not sophisticated, no chips in key fob. They stuck a tiny resistor in the key that has to match a value in the Theft Deterrent Module (TDM), or BCM on later LT1's. PITA as it relies on physical contacts in the ignition key chamber. By the way the TDM or BCM also picks TD relay that allows starter solenoid to pick. Your custom starting setup must eliminate and bypasses all that.

I have a bench top harness that uses the pins above. I built it to play with and test different software products on my spare PCM, runs off an old PC power supply.

By the way if you need wiring diagrams here is a link to the '94 service manuals, close but not exactly the same as the '97 .. Go to My Files , select 94FB folder , select 94 scv manual vol 2 of 2 for the PCM and wiring diagrams. Go to page 8A-202-6 for C220 cavity and page numbers on right of table directing you to detailed diagrams.