swapped harness from 1.5 to obd2 car wont start help !!

[Rettax3]

ok guys here where I am at hooked up a scanner and scanner says no link so wont read the computer idk why. But we hooked up a light on the injectors wires and they are not pulsing or blinking. I have power to all them but no ground. Ok so I poked around the ecu plugs with a test light to see if there was power there and when I was doing this I found the one what would normally ground that injector out and the light that we put on the injector plug lit up. So this is telling me I have a ground issue correct??

I'm not sure how you set your test-light up. If you are looking for battery + coming through the injector then to the connector in the PCM's harness, that tests the circuit. BUT, the PCM provides ground to that circuit inside itself in timed pulses, thereby completing the circuit and allowing the injector to fire. Without the engine running or cranking and the PCM working, there will NOT be a ground for the circuit, otherwise the injectors would just stay open constantly and fill the cylinders with fuel. Also, some incandescent test-lights will not illuminate on the injector plug either, so that isn't 100% definitive, unless you were using actual noid test-lights designed to test the split-second injector pulse. Test the PCM case to the car's ground with a multi-meter -don't bother with a test-light, as it will again be inconclusive. You need to be sure the PCM case has a good, clean continuity to ground (no more than 2-4 ohms, or it may be grounding through a sensor, not an actual ground). If the case ground is good, it is a safe bet the computer has a good ground, and you can stop chasing wires in that direction.

There is a mechanical problem that could, in theory, cause this, rather than an electrical one, but it is a serious long-shot. When I bought my '89 RS Camaro, I got the car without engine or transmission. It had Headman headers, a 2.5" or 3" high-flow cat, 2.5" exhaust and a Flowmaster 80-Series muffler. It had also been upgraded with the rare Borg-Warner 9-bolt Posi/Disc rear-end, and a tubular-steel torsion-bar setup, and decent 16" rims, all told the upgrades were worth more than what I paid for the whole car. Anyway, I had an '89 Caprice Police Special Detectives' car 350 sitting around and looking bored, and a complete 5-speed setup without a home yet... And now to my point... Although the engine ran perfectly when I bought it, it had sat around for a couple of years until I ended up buying that Camaro. When I installed it and hooked everything up, the engine wouldn't even fire. After a couple of days of tracing and re-tracing and re-tracing again, I finally figured out that ALL OF THE INJECTORS had siezed-up while sitting. I replaced the injectors and vroom, I was in business. Whether the donor-car had water in the gas-tank, or what, I don't know, but even my 'old' '88 Camaro's injectors once sat long enough to sieze-up, and I had to tap them with 12-volts a few times to get them operating again (only TAP the injectors with full-on 12- volts though, they are not meant to run full-on, and the solenoid can fry on them in a few seconds). A long-shot though, still a possibility.

[3X00-Modified]

Did you follow all of my directions on what to do to the harness before using it?

Double check the pins on the injector harness plug from one to the other and make sure they are the same. I thought they were but they may be pinned differently.

[beretta777]

I was using actually noid lights got a friend that is a diesel mechanic and he lend them to me. Now as far as the pcm case it mounts in the car with a plastic case how does that ground it ??

[beretta777]

Did you follow all of my directions on what to do to the harness before using it?

Double check the pins on the injector harness plug from one to the other and make sure they are the same. I thought they were but they may be pinned differently.

Yes I did but did not rewire for a tach or rewire the abs just swapped main harness and injector harness for the 3 wire temp sensor. and wired the com port.

[3X00-Modified]

Did you do the wiring that was necessary for the MAF sensor?

The ECM is grounded via the harness it has ground outputs that are bolted down at various locations, one being the stud to the trans under the exhaust and the other being another stud for the trans by the starter.

[beretta777]

I plugged in the maf did not wire anything.

[Rettax3]

I was using actually noid lights got a friend that is a diesel mechanic and he lend them to me. Now as far as the pcm case it mounts in the car with a plastic case how does that ground it ??

The computer has points on the internal circuit-board that ground the case, so if the case has a good ground, it is through the grounding-wires, easy test. If the grounding wires are compromised due to grease, corrosion, etc, the case won't have a clean ground signal. One of my cars has the ECM grounded via a strap on the computer case, because the ground-wires to the block got disconnected and are hard to reach, so the case ground was an easy temporary fix -that was well over a decade ago.

Most likely, a wire got cut or crimped or missed, or the PCM has anti-theft enabled, or was somehow damaged during the transfer. Do you have the other PCM you could plug in to see if the car will run off of that to eliminate a PCM failure? These things are metaphorically bullet-proof, so it seems unlikely to be that, but...

Here are your essential wires needed for the '97 Lumina PCM:
Battery + C1-20
Ignition + C1-63
Ignition + C1-19
ICM C1-53 (white)
ICM C1-52 (tan/black)
ICM C1-44 (purple/white)
ICM C1-45 (red/black)
MAP C2-12 (light green) -check the MAP's other two wires, one should be ground, the other should get ~5v+ reference.
Knock C1-33
MAF C1-54 (yellow) --check the MAF's other two wires, one should be ground, the other should get 12v+.
F/I#1 C2-28 (black)
F/I#2 C2-30 (green/black)
F/I#3 C2-32 (pink/black)
F/I#4 C2-22 (blue/black)
F/I#5 C2-24 (black/white)
F/I#6 C2-26 (yellow/black)
With a good ground, power and ground to the ICM, and proper fuel pressure, a healthy engine SHOULD run with these hooked-up to the PCM.
You will also want the Cam and Hi-Res Crank sensors hooked-up, but it SHOULD run without them:
CMP C1-5
CMP/CKP C1-57
CMP/CKP C1-18
CKP C1-4
ALDL C1-15 (tan)
ALDL C1-59 (purple) -you will also need to supply battery + and ground to the ALDL for it to function. I don't have the pin-outs handy for it, sorry.
Eventually, you will also want the TPS, IAC, IAT, and ECT, but the top list are the essentials to get started. Since you are not building the harness wire-by-wire (I did that on my '90 turbo 'Retta using OBD2 for the LG5 3.1/VIN-E 3400 hybrid, I actually much preferred doing it that way to having lots of extra wire and little dangling connectors to nowhere all over the place), just check these primary wires and you should find your problem if it is in the harness or the car's interface into the harness. Good luck.

[beretta777]

Ok just went over the two grounds on trans and the one on the firewall took them off clean them and put electrical grease on them all. I tried both pcms the 97 and 96 both don't make a different. How do I test the case to see if its grounded?

[beretta777]

I guess where I am at now ill start tracing wires from the injectors to the computer to see if I pinched or broke a wire when swapping from car to car. I don't know what else to do.

[Rettax3]

Just use an Ohm-meter (or multi-meter) and check continuity to the negative battery terminal and/or the engine itself. Especially on cheaper meters, do a 'probe check' by seeing how much resistance the meter measures by touching the probes to each other -it is not uncommon to see a few Ohms of resistance measured on the probes themselves, this is more of a mis-calibration of the meter itself. Then check the PCM case as mentioned, the reading should not be more than a few Ohms higher than the 'probe-check' reading. If you don't have a meter and don't want to borrow one, Harbor Freight Tools usually have cheapies for sale for ~$5 -they are worth it just to have something to toss into the glove-box. If you are going to do a LOT of this kind of stuff, invest in a Fluke or other quality meter, but the cheapie would get you by for this...

A test light will not tell you if the ground continuity is clean enough, or if the resistance is high enough to indicate that the PCM is grounding through a sensor, like an O2 sensor (which earlier ECMs can do, then you have all kinds of trouble once the computer switches loop-modes, I'm not certain an OBD2 PCM can do this though).

But yeah, I would start checking the wires at the PCM connector, make sure you have signal/continuity/voltage where you are supposed to. It takes some time, but you really don't have that many wires needed for the engine to run. Like I said, the low-res 7x crank sensor at the back of the block is the only critical one (although I've worked on a couple of these engines that would not run without the hi-res or cam sensors plugged in like they are supposed to), and with spark, you already know that is good. So long as the PCM has the three power wires correct, good ground, all four wires to/from the ICM plugged in and the injector wires, it should at least cough for you.

You are certain that you have fuel-pressure at the rail? You've done a fuel-pressure test and gotten ~47 PSI? Too high a pressure and maybe the injectors can't open, too low and there wouldn't be enough fuel present in the cylinders...

[beretta777]

Ok I do have a o2 sensor unhooked the one that is right behind the cat I don't think the 94 had this and I didn't change it from the 96 so maybe it needs to be hooked up to be ground the pcm?? just a thought.

[heavywoody]

Nope; that one doesn't matter for grounding purposes; it will just throw a code unless you've disabled that code in the PCM.

[beretta777]

ok but what do I actually poke with the multi-meter on the case sorry stay with me pretty slow when it comes to electrically stuff

[Rettax3]

Any metal place on the outside of the case with one probe,any metal point on the engine with the other probe. All you are doing with this test is making sure that the computer has a good clean ground. Since the computer is connected to its' own case (electrically speaking), if the case shows a good ground, the computer has a good ground.

When I mentioned the O2 sensor, that is a little different thing, let me be more clear on that: When the ECM is in 'Open Loop Mode', meaning that the O2 sensor is not hot enough to read the gasses in the exhaust-stream correctly, the computer is using a set of calculated program tables to deliver fuel to the engine -usually a little rich. On some of the older systems, the ECM can get a false ground through the O2 sensor (it works fine, but that isn't where the ECM is supposed to have its' only ground). The problem arises when the ECM switches to 'Closed Loop Mode' once the O2 sensor is warm enough -then the ECM starts reading the voltage generated by the O2 sensor, and can no longer get that false ground, and if there are no other grounding points the ECM can no longer function. Since your '96 harness uses a heated O2 sensor, the PCM may not even be able to ground through the sensor, I don't know as I haven't seen a grounding problem on an OBD2 car like the one I experienced with the older GM ECM I mentioned. Don't worry about the O2 sensors right now, the engine can at least run without them. Getting it running right can come later, after you get it running...

[Slinky]

I obd2 swapped my obd1.5 retta over 2 years ago and never plugged in the heated o2 sensor, runs perfect