Yeah I hear that, I've been looking for a set most of the weekend and today. Been trying to find a good used set, but that's not looking so good, I'd rather pay more and be sure that a coffee spill didn't wipe out a page or so of some info I need. As far as the voltages and such, they are the same @ the component as they are @ the pcm like I figured then? I just had to ask, cause these cars throw curve *****, one other thing. Other than not unplugging or plugging in any connections with the key on, is there anything that I should definitely do or not do?oh continuity testing, I need to verify that the particular circuit is 12v, and not below 12v, that I still have in my head. Any suggestions on where to grab a set of the manuals? Thanx, for the help

 

Ok so u guys keep suggesting that people invest in an ALDL 12 pin connector, and get tuner cat or another scan program. Well I've been kicking this around, well I was browsing on the net and I started looking for an obd1 cable with a usb plug on it. And of course I found some different versions. But one in particular even comes with a cd rom with a bit file, and a scanning and programming program. Any body else ever hear of this? Less than 100$. So what's the catch? U get to use the programs x amount of times and then u have to buy the program? Or is it open ended, just registers to one car via the VIN when it makes contact with the PCM? I would just like to know. Sounds too good to be true. Also has anyone used this cable and cd rom package? How is it? TIA.

 

First off, your vehicle has a PCM not an ECM.

If you want an opinion regarding something(referring to the cable and software), it would be better if you provided a link to it.

As far as manuals, this is where to get the factory manual.

http://www.helminc.com/
Perhaps a quick trip through craigslist or Ebay will turn up a used one as was suggested above.

As far as alternatives to scanning. Here is a reliable source for cables and links to software.
http://www.aldlcable.com/

As far as your problem, you have to separate the rest of the vehicle from the tranny. That is, you have to get to the point that you know it's either tranny or something else. In my mind, you haven't done that yet.

But then we get back to scanning capability. Like the title suggests, if your vehicle is truly doing as you said in the first post, it would leave a trail of either codes or real time data to indicate why it's doing so. So in depth scanning capability is a must.

Here is 2 simple suggestions to do, without having books and scanners.
Aamco has something like $39 diagnostics. Try it out. Even if they don't tell you anything useful, it's only 39 bucks. But just maybe they will tell you something that can help.

The other is a line of parts suppliers called Auto Value that can reprogram your PCM. Usually they can tell you if the PCM is a problem at the time they reprogram it. If nothing else, they can at least get you to the latest version of firmware. If there is a problem with the PCM (note here), they will reimburse you the programming charge toward the cost of a new PCM.

The note I mentioned above. I have never EVER actually witnessed a defective OBDI PCM. So don't put a lot of weight on the possibility the PCM is defective.

Last thing and I'm gone. Just skimming through my shop manual came to this. Low system voltage, DTC75. NO TCC, Max line pressure. Third gear only. Code is set, NO SES. Code goes away when condition goes away.

The voltage to the PCM is monitored as well as transmission temp.

Other trans codes can have the same 3rd gear only effect.

IMHO you have a tranny issue and this post should be in the drivetrain board.

 

Look in the computer forum at the sticky for Tunerpro RT. It's free. Other than that, I would go with the Tunercat/Datamaster bundle you can get on the Tunercat website.

 

The car has been scanned, 5 times now. As of 8 pm last night. NO CODES. When I first got the car and it lost the a solenoid, didn't know that then. And the idiot that was supposed to be a great mechanic said get a new one or rebuild this one, I bought the current tranny. Now a snap on, an otc, a new matco and even a tech one have come up with no codes. And an a solenoid is definitely a code right? Well chevy scanned it then, and no code even then. So the tranny has been pressure tested now, the a,b,3-2, absolute pressure manifold, and tcc solenoid, and the pressure switch all changed. The tranny fluid and filter changed. But nothing on the magnets, a very small amount of shavings. Did the solenoids to try to see if it would change anything, it didn't. So I've been pulling the pan to inspect for clutch material and nothing. The tranny checks out, the tranny is getting power. So according to what I've been advised, tranny is not the issue. So here's another little part of the puzzle. DEFAULT, can be the pcm, as I've been calling it, losing most of it's inputs and running everything in a safe setting that's established in the pcm. But according to the dH
ealership, default can be the engine being shut way down by the pcm, still having 4 forward, and reverse. So no effect on the tranny other than poor engine performance making it seem that way. And the pcm can put the tranny into limp by it's self, no loss of engine performance. And it can be a total flush, tranny in 3,2 on manual selection, reverse. engine can be practically shut down, no horsepower, timing rolled off, injectors barely operating, so forth. So here's my situation, chevy here doesn't have a portable scan tool for logging since their fire last year, my car is 100% @ start up, take off and stop, tranny default. Continue on for even a short while, my engine starts to get a slightly different idle, but still a lot of power. After 5 mins, it sounds fine, then sounds "turned down" again. But it will still spin the tires in 2nd like it's nothing. So I've spent all day yesterday running wires, doing continuity tests, looking for any signs of fraying, and also finding out about the cable I need. Supposedly from what the description says this is a gm cable, and the cd rom is from them as well, that's why I asked if anybody else had heard about this. So the cost of having the car scanned, that's not an issue. And trying to ascertain if it's the tranny or if it's something else hasn't been so cut and dry. With everything looking like it did when I had the tranny inspected, pan off and all, I have been told that it's not the tranny. And the fun part about all of this is the fact that the mechanics around here aren't trustworthy. So I stay and watch what they do and I stick around and watch what they do. So if the tranny tested fine, and I'm running wires and checks on EVERYTHING, what do u think now? One final thing, I was pissed @ the car 3 am this morning and it was time to wrap up another night wasted. The car was running, I taped the pcm, and the car died, I didn't beat the hell iut of the pcm, I taped it not as hard as I wanted too, but it wasn't as hard as I knock on doors either. So now that that happened I looked up signs for a bad pcm, and that's supposedly one of the tests. But I tried to replicate this an hour or so ago, and nodda. I'm really tired of this

 

Hey now get this. So I brought the car to a dealership and kidnapped a tech, we took the car for a drive with the scanner plugged in, about damn time, every other time I suggested it they didn't have an available scanner or tech. Now isn't that getting what u paid for? Well the scanner said everything was ok until we hit the brakes, then the pcm just stoped communication with the scanner I guess. No readouts of any kind. Up to that point there was no indication of any problem. We shut the car down for 30 seconds, restarted it, then the pcm was communicating again, we didn't move and I hit the brakes, the pcm still communicating. Started off, hit the brakes, still working, shift into second, brakes, still working. Speed up to third gear and hit the brakes, poof pcm was gone again. Now what in the heck could've made that start happening all of a sudden?? And does this mean the pcm is shot? Or does it mean that I need dynamite? Lol. Everybody was scratching their heads. Any ideas??

 

congrats on getting a little closer to the problem.

There's a very common problem that has been known to cause issues similar to those. The battery hold down on these cars always breaks off and the battery moves around under hard maneuvers like accelerating, cornering and braking. The battery positive terminal momentarily touches ground.

Either secure the battery temporarily until you can get a new washer reservoir or wrap it with something insulating and give your experiment another try.

If that is not the problem, look at the system voltage to see if it's momentarily going lower than about 10 volts. Seems something is shifting to cause this problem. I highly doubt it's the PCM although a loose solder joint could be an issue.

Try wiggling the connectors ALL of them not just the ones at the PCM.

 

Ok so wiggle the connections everywhere, ok. Makes sense. The battery was actually my first thought. My hold down is in place, and working. I see what u mean about that happening though. It actually happened to me when I first got the car, but I was able to figure it out only because it stayed in contact and upon opening the hodd @ night I saw the arcing. I got some red rubberized plastic and fashioned a wrap that goes around the wires right there. Now I know I can't be applying power to wires @ the pcu, and the pcu harness is in a tough to get to spot, so pull the pcu out and start wiggling. Um one more thing, I have 2 bundles of wires the run right down by the passenger side headers, they've been heat taped, and it looks like they haven't been touching. But as hot as our headers get, couldn't the heat even with the cheap heat shielding tape, cook the wires? I have a pic of the location of the wires, apparently the wires should've been extended and rerouted? I would've thought that would be basic common sense, and by the looks of one of the sets of wires, they run back along the inside of the subframe, a big purple wie and some others. Probably a safe bet to start there. Even though they run back, the trans wires all come out back behind the engine, in a wire bundle by the dipstick and come together with other wires and the vacuum line for the fuel pressure regulator and the hvac, by the purge solenoid. Any helpful ideas???

 

Oh one other thing, I'm in limp, there should definitely be a code being set, so I'm wondering if this pcm wasn't programmed before I had my tune uploaded to it. My tune has been taken back off, I have the stuff to do that. So if it's not showing a code, then perhaps they tuned the ses out of the car? It's odd though because of what's going on, but if I disconnect the maf and start the car the ses comes on and so do the fans. But that code goes away all togther if I shut of the car and plug it back up, and fire it up. It should still have the code listed right? Not just poof gone??? And the sensore that will typically put u in volumetric efficiency mode are typically the MAF, the MAP, IAT, O2's and the coolant temp sensor on the drivers side head? Is that correct? But that's for engine, which it also sounds like is being gunned down. Still have tons of power, u can feel it, but u can hear a major change in the exhaust note, it goes from gig and open with the lope that I always here from these cars, to sort of like, it's hard to explain, the sound is similar, just a lot more mild? Idk it's tough to explain. So I guess what I'm asking is can I fined that out? Shouldn't chevrolet have been able to find that with the tech tool? I'm @ a loss. Would sure love to get this done and overwith.

 

As always all help is appreciated. Need help here. My rope has run out and somehow it's around my neck lol.

 

The PCM would only default to speed-density (using the VE tables) if it lost the MAF sensor. If it does that, it needs the IAT and MAP to calculate the mass air flow. The O2's have nothing to do with whether its running MAF or speed-density. They are just there to correct the A/F ratio, in either mode. Not sure why the CTS would put it into speed-density. No logical reason to assume that,.

 

ok that makes sense because the difference in a 93 and a 94 is that the 93 has no MAF and runs on the tables or speed density and the 94 has a MAF. So what do u think? Wiggle wires, makes sense, but is there any way you can tell me to start narrowing this down? There's a lot of wire in these cars, and I've been running wires all day again. I'm not putting any charge to them cause I don't want to fry a circuit or the pcm. Thanx for the info, it's logical, yet I didn't have a clue

 

The bundle of wires running down the passenger inner fender was my problem. Although it looked fine, the wires inside were burned crispy. The wires in there are the right side O2, the knock sensor and the starter engagement wire.

My O2 wire was burned apart and never got a code. Car ran like crap while it was in closed loop. The PCM thought is was running rich and so it continued to pull fuel until it ran so crappy it jumped into open loop momentarily. Then it would go back to closed loop and start the entire process all over again.

There is an easy 2 step process to confirm this is the case, but I think you should just inspect and then move those wires.

Incidentally you alluded to having a code and NO SES. There are a few codes that set but do NOT set an SES. One that comes to mind is the DTC16 which indicates a loss of the low res feedback signal from the opti. This will shut the engine down but never set an SES.

One last thing: Did you bother to check the system voltage when you hit the brakes to see what it is doing?

 

I did check the voltage, that was fine. Actually what I meant was I can do just about anything to my car and no codes, so I think they tuned the codes out$ I'm going after that wiring bundle right now. So wish me luck, and I'll let u know how it goes, talk to ya in a little while. Thanx for the info.

 

Well now, isn't this just interesting, the pos cable on my battery has been contacting stuff, though I thought it had been insulated well enough, and not moving the car, but scanning with a friends scanner, then slowly, like grandma slowly, driving the car has revealed that I need a new pcm, after it goes through the first upshift, then it goes all to crud, so pcm anybody? Where can I find a pcm? May as well get it tuned and setup for my vin and stuff too. Does pcm's for less sell pcm's? Or do u have to find one and send it to them?