1995 3.4L Camaro No ECU Response

[Robindehood]

I need to get this sorted out, with a baby on the way it's just time.
For those seeing this for the first time and don't want to look at page 1, I've got a 1995 3.4L camaro engine that I'm trying to tune and I'm struggling to get the PCM to communicate with my ALDL cable and Laptop. I'm using Scan 9495 v6 for all my scanning.

I'm going to go back to basics in the wiring and see if I can't get it to read anything off either PCM.. At it's basics, the ONLY wires that need to be connected to the OBD port are power, ground and the serial data line correct?
So orange to the battery,
Tan to the Serial Data Line off the PCM,
Both blacks to a ground. From what I've been told, they can share a ground and it won't affect it either way. (If anyone can confirm that would be great)

I'm using a Red Devil River ALDL cable. I've followed several guides on the drivers, and there's so much back and forth info given on which ones work and don't that I'm not even sure which threads to trust.
For those seeing this for the first time and don't want to look at page 1, I've got a 1995 3.4L camaro engine that I'm trying to tune and I'm struggling to get the PCM to communicate with my ALDL cable and Laptop. I'm using Scan 9495 v6 for all my scanning.

[kur4o]

First[for testing purposes] Get flashhack program from steveo website. It is the best comm tool for obd1. It will help you narrow down problems faster than anything else.

For the pcm you need to wire
B16-ground
B14 - B+
C3 - Ign
B19-serial data

B=black
C=blue

I am suspecting a defective cable. or wiring issues. This pcm needs good solid ground for flashing. Also I don`t suggest flashing in car. It is very sensitive. Setup a bench with fully charged battery.

[Robindehood]

I have his flashhack program downloaded, currently just telling me I have aa "Silent Bus" when I try and read the pcm with it.

I'm leaning towards wiring issues as the cable worked once, and I made a couple routing changes to the wiring and it hasn't worked since. It's attempting to track down the wiring issue that's giving me such a headache which is why I've resorted to trying to just splice in the needed wires in the engine bay and working from there.

I dont think I'm currently trying to flash, just trying to read the data already on there so it's just a read if I'm not mistaken?

[Robindehood]

Gonna give this a bump as it's still an on going issue. Starting to wonder if it's a pc issue vs cable/pcm. Anything I can check on that side of things to potentially get this resolved?

[Robindehood]

Trying to dive back in on this after a few weeks away from it.

Using ALDL-Test V230 I've confirmed that the ALDL cable is working on the laptop side of things. It passes all the tests, and I've also used Realterm to verify that it's working on the pc end correctly as well.

Using ALDL-Test I've confirmed that the grounding is good, I have continuity from the PCM serial data line to the serial data line on the obd port as well.

When trying to use Steveo's flashhack tool to ensure the cable is connecting, things go a little south. This is what it says:

Reconnecting to ALDL bus, please wait....
DEBUG:Listening for ALDL heartbeat to determine current bus master...
The bus is silent.
DEBUG:Trying to reconnect to bus...
DEBUG:Trying to reconnect to bus...
DEBUG:Trying to reconnect to bus...
DEBUG:Trying to reconnect to bus...
ERROR: Error reading mode2 segment 0[40]
ERROR: Could not complete read procedure

Despite failing this, I attempted to use the program Scan9495-V6 from Gary Doug. It also failed, giving me this error:
Response: cs=80 Bad checksum!

Could really use some experienced vets assistance on this. Can have door dash or whatever your local food delivery service is drop off a case of beer for your troubles

[steveo]

something is wrong with your tests, as if the vehicle wiring was truly okay and the aldl cable was truly okay, it would be working with some the many software packages you've tried

are you 100% sure of your tests on the vehicle wiring? or just 99% sure

if so, the only reasonable conclusion i can draw then is that the aldl-test program that i have never heard of before is not a truly good test of your serial interface and the cable is faulty.

it's totally possible that the aldl-test program is just a dumb thing that ensures a serial port can be set to 8192 baud and that the data loops reliably between rx and tx, which would prove your driver works and it's actually an aldl cable, but doesn't prove that there isn't something broken between the serial chip and the external data pin on that cable.

[Robindehood]

Yeah, at this point I'm truly just at a loss. I've tried full on cutting the OBD port out of the car and wiring it independently. Grounds are good, it's directly to the serial data line at the pcm and still nothing.

[Bent72]

I'm leaning towards wiring issues as the cable worked once, and I made a couple routing changes to the wiring and it hasn't worked since. It's attempting to track down the wiring issue that's giving me such a headache which is why I've resorted to trying to just splice in the needed wires in the engine bay and working from there.

This stood out to me. I know you tested for continuity, but sometimes broken wiring can pose strange side effects

Since you now have 2 ECMs, are you open to building a harness to do this on a bench? Looks like you’ve tried everything else

[Robindehood]

This stood out to me. I know you tested for continuity, but sometimes broken wiring can pose strange side effects

Since you now have 2 ECMs, are you open to building a harness to do this on a bench? Looks like you’ve tried everything else

What all do I need?

[Bent72]

I’ll be honest, I’ve only done test benches for other applications, but looks like post 17 above has at least some of that information

[Robindehood]

Yeah I'd be open to giving that a shot. I'm also inclined atm to just use this stock tuned ecm that I picked up along with a set of the stock 3400 injectors and see how it runs with those. If it at least runs, I can stop getting so damn demoralized about not being able to plug it in right now