The way the problem appeared:
Up to the time this happened NO problems of ANY sort had occurred. No missing, no stumbling, no hard starting, NOTHING!!!

Driving 55mph for approx 5 minutes w/cruise control on. With no warning, the engine dies. I look at the gauges and see SES and "Check Gages". I coast to the side of the road and look quizzically at the gauges. Nothing there to look at except the aforementioned SES/Check Gages. I try to restart and it cranks perfectly but does not fire. I'm thinking, of course, Opti. I pull the PCM BATT/IGN fuses for 20 seconds, and then reinsert them. Crank but no fire. Crap.... I try restarting it several times. About the 15th time, it cranks and fires. The SES and Check Gages lights are off. What in THE hell.... So I drive it to my daughters school (about 5 miles) , then return home (15 miles). It's running flawlessly. I wondering what in the world had happened. I take my daughter BACK to her high school for her basketball game. I go to get on the highway and, POOF! it's baaaack....
This time, I crank about 25 different times with minutes in between the checking of fuses, relays and anything else I can think of. It NEVER hits. Dang. I call a wrecker and have it towed to the house. I didn't have my LT1 Edit cable (it's in Houston, I'm in New York) so I ordered a new USB version from Andrew Matteri and once it's here, I hook it up and, to my horror, there's no SES codes displayed although the SES light is still brightly lit. Dammit! Futher puzzlement is that the 'Desired Idle' is displayed in the PCMCOMM screen as being a ridiculous value of 3,188 RPM. I check every fuse again but nothing is wrong there. All are intact. So.. I decide to do the PCMBATT fuse to reset the SES and see if 'something' somewhere will trigger it and perhaps I can capture it then. WTH? It won't reset! As SOON as I turn the key on, the SES is there. Nothing is triggering this bish by mechanical activity, it's there at "Key On". So I try resetting it via PCMCOMM's 'clear DTC' command. No effect whatsoever. I try Datamasters Clear DTC's. No effect whatsoever. I disconnect the farking battery for 45 minutes. NO EFFECT WHATSOEVER. I'm thinking the PCM must be bad since the 'desired idle' was that silly 3188 rpm and no resets available on the DTC/SES. I go order a PCM, trade in my old one for a total outlay of $128. Not bad (if it fixes the problem. It doesn't...) Unfortunately, the same situation. Glaring SES as soon as the key is on. So, deducing that it might be a wiring harness against the Hooker Headers, I look there. Viola! (I think... sigh... keep reading ) there are a total of 4 bare wires showing. Two from the drivers side O2 sensor, one from the PCM Ground and the STarter solenoid wire. I section in about 4' of wires in some split loom and put on some weatherpack connectors. Afterwards, I try to start it. Fark,
it's still the same problem. I think, "maybe the short in the wires fried the new PCM....". So I get another PCM, That was this morning. I plug it in. I try to start it. Same Problem. SES light, 3188 desired Idle, Can't reset the DTC's.
I'm really surprised the shorting wires didn't pop any fuses at all. I'm guessing now that there is a short in the wiring harness somewhere on the wires going from the shorted bundle (Passenger side O2, Knock Sensor, PCM Ground, Starter solenoid) to the PCM. Any of you have any insite on potential errors? I put a volt meter to the Passenger side O2 sensor harness.. Here's what I got....
Black Wire = 12 volts (since this is supposed to be ground, not good. I pulled the fuse for Fan/ACTR, then reinserted it and this time got zero volts. What the....?)

Purple wire = .87 volts

Tan wire = 1.57 volts

Brown wire = 12. volts

No voltage appeared at the PCM ground

 

Sorry to hear about your problem. I would try starting with the basics. See if your getting fuel and spark and then go from there. Can you hear the fuel pump when you turn the key to the run position?

Brian

 

Yes. Fuel is working fine. You can smell it when you crank the car and the tips of the plugs get wet with fuel after cranking it. The things that keep bugging me are that the SES light cannot be reset in anyway and the "Desired Idle" of 3,188. I've reprogrammed these cars and several others around a hundred times and I've never encountered either of these conditions before. It's snowing here today so I won't be able to get out and pull off the split loom to find it just yst. Thanks for the response Brian

 

Isnt the Check engine light is supposed to be on any time the key is on and the engine is not running? For example, if i go out to my car right now and turn it to the run posistion, but not start it, my check engine light will be on, even though there are no codes stored in it. Is this what you are seeing?

If it was an ignition problem, such as yor opti, it could go fail suddently and no DTC could be thrown.. Thats what happened with mine. After the engine dies, the check engine light will turn on automatically, but if something happened real quick, it may not have thrown a code.

I would start by using a spark tester and see if your getting spark. Go through the basics first. If your getting fuel (which it sounds like you are) and your getting spark. It should at least attempt to fire up. -Jeff

 

Yeah you are getting your mind twisted up over this SES light when its completely NORMAL! Any time you just turn the key to the ON position the SES light will glow... now if its blinking then you have problems(bad PCM).

I cant believe you havent checked for spark though. Thats the first thing you should be doing maybe next to reading DTCs which youve done.

But if I had to guess Id guess at the coil or ICM or bad connection at the opti.

I dunno what to tell you abou the desired idle value unless you have the wrong version of the data logger.. is it LT1 edit or TTS Datamaster. I dont use LT1 edit so I dont even know if they have that option.

 

Ever figure it out man? I'm curious is to what it was. -Jeff

 

Not yet. It's been too cold here in upstate New York for those unfortunate enough to be without a garage. Tomorrow will be a comparatively balmy 40's so I'll be out checking wiring. To address the other poster, the spark was the first thing I checked. As far as the SES light/Check Gages, my '96 would only flash the light during a diagnostic read of the sensors, then go out after a couple of seconds. I would've swore the '94 did the same but perhaps not. The reason I don't think it's the opti is that when it died the first time, after many cranks, it started right up perfectly and ran perfectly till about 25 miles later when it completely died again.

 

when it dies does it stumble a little first, or just shuts off???

 

It dies in a lightswitch like manner. Runs perfectly, then, as if you'd turned the key off, it dies

 

I was having some problems with mine a while back with it dying and stuff. I could start it and let it idle in the driveway for like 1-2 hours then it would all of a sudden die!


Wouldn't start, wouldn't start, wouldn't start...then all of a sudden it would start.


Ended up being the opti harness.

 

Thanks. I haven't got mine figured out just yet. Too much stuff going on. I had heard about;
1. Coil wire going bad.
Checked that. Looks fine (not corroded,etc)
2. Opti harness connector at mid intake connection.
Pulled it apart and looked at it. Seemed to be fine.

I got some GREAT Pinouts from a fellow list member regarding the PCM the 4 connectors. It lists the sensor they connect to and the expected voltage readings for Key On/Key off. I'll check that next. Certainly, I'll post whatever the hell it is.

 

Shoebox has the PCM connector pin-outs for the 95's on his website. The connector pinouts are marked to show the differences for the 96/97's:

http://shbox.com/1/4th_gen_tech2.html#1995_pcm_pinouts

Also the wiring diagrams:

http://shbox.com/1/4th_gen_tech2.html#1995_pcm_wiring

 

ya man when the car dies and isnt running of course the SES light is on. it always does that to tell you that the light bulb isnt blown. its the self test feature of any car.

your problem did not throw a code which is why you cant pull a code out of it.

don't waste ur time playing with that.

 

Maybe I'm just used to my '96 and the '94 is different in this respect but when I turn the key on (but don't start it) in the '96, of course the SES lights up to let me know the bulb works, etc. But if I wait a few seconds, the light goes out. If it stays on, I have a stored code. On the '94, which I have only had about 10 months, it may be different.

 

dave.. i believe you are correct.. your 96 has obd2 which does the self test when you turn the key on (every obd2 car does) but your 94, being obd1 isn't as involved as the obd2 is.