You can buy scan tools that will scan and record the data from the ECM and the CCM as well. Ease Diagnostics sells them.

 

Mike - Currently I am working with some scan tools mainly a laptop and 7 programs that I am trying to get to work. I built the ALDL 2 transistor interface box and have got 2 of the programs to respond somewhat. Going to take it on the road tomarrow and out of the garage. I have tried to get some advice as to what programs people like and use but I did not get much back from the scan and tune Forum. If you have any advice I am all ears.

 

I am thinking about getting this one:

http://automotive.miragecorp.com/Pro...ISoftware.html

I am going to have to review what monitoring and recording capabilities it has.

 

i havent forgot about you guys. my plan this weekend is to ( the program will let me print the diagrams ) print the diagrams scan them then post them. let me know now if this going to be in some way a violation.

 

I use and sell Ease Scan Tools. You can check out their site at www.obd2.com They have a laptop based scan tool for GM OBD1 and OBD2 versions specifically. They are a partner with GM and also sell "official" GM PCM reprogramming software. The reporgramming software uses only GM supplied BIN files to upgrade the stock PCM programming, (no tweaking unfortunately).

I use the Pro version now that I'm a rep., but I originally started by buying the Personal GM OBD1 version and using it on my 88 to fix an intermittant problem. Unless you own a shop the personal version is the way to go. Ease is not cheap compared to other scan tools, but the OBD1 version will scan pretty much eveything GM made that was OBD1 from 1982 - 1995. I'm talking GMC/Chevy trucks, Caddies, Saturns, you name it. The parameter sets for the 93-95 Vettes include the ability to scan the ABS/ASR and CCMs as well as the ECM/PCMs. There is one year of free Tech Support from the date of purchase. As a member of the Corvette Forum I give a 10% discount to CF members who order through me.

The one big advantage I find with the Ease OBD1 tool is that the ABS/ASR & CCM parameters can be scanned where most of the cheaper alternatives don't do that. There are several other very good ECM/PCM scan tools available for free or cheap on the web and often that is the more cost productve choice if you only want to scan the engine operating conditions.

Check out the Ease web site and others available on the web too. If you want more detailed info, send me an email and I'll be glad to send you a write-up I did in html showing screen captures from actual use of the tool on my 88 OBD1 Vette. I originally used the tool to pin a problem on a bad ECM. I figure that I and saved myself the cost of paying a dealer, so at $315 for the OBD1 tool, I have fixed my problem for about what the dealer would have charged, and still have a powerful scan tool for ongoing monitoring.

Ease is also the ONLY laptop based scan tool officially recognized by the California Bureau of Automotive Repair for smog shop use. I know this because they told me so when I sold them the latest upgrades. Works on all Windows platforms Win98 - XP.

 

Mike,
I've contacted you before regarding EASE. I'm a big fan of the product and have recommended it to folks that have purchased. I'd been looking for a DIACOM+ replacement to use when my old laptop finally bit the dust. I really wanted to go with EASE but the limit of 20 different vehicles for the Personal version is a sticking point. As a club member, I scan many cars for different people. I'd go through the 20 in one weekend at a big event. I don't know what an additional 20 would cost, but I'd really need the Professional version to carry on with what I do and I couldn't swing the cost of the Pro version. It's too bad, because I really believe EASE is a superior product, just out of my price range for what I do.

 

Ray, Ease Personal scan tools now allow for 30 unique vehicles to be scanned before a scan license upgrade is required. For most users the 30 unique vehicle limit isn't an issue. I've run into others who belonged to a club and wanted to scan a lot of cars and there are some misconceptions concerning the tool license limit.

The 30 unique vehicle license limitation upgrades are $75. If you asked anyone who wanted a scan to pay you $5 for the scan setup, you would easily collect twice what you need to upgrade for another 30 unique vehicles. Once a vehicle is in the database, all future scans of that same vehicle count only as that 1 unique vehicle license. You can scan the same vehicle a thousnad times and it only uses one unique car license of the 30 available.

So, if you setup 25 club vehicles and charge 20 of them, (say 5 are great looking babes, buddies who supply beer, or club VIPs), then you have $100. That is more than enough to pay for the next 30 car license upgrade and you still have 5 car licenses left for yourself. Remember, from then on, you can rescan any of the original 25 cars any number of times for no additional license usage. Also, other club members who might purchase an Ease scan tool can swap their scans with you. Scans loaded for review and playback, but not made by your tool directly attached to the scanned car do not count in the 30 unique license limit either.

-Mike

 

i was able to scan and save in the pdf format ( acrobat reader ). let me mail it to who ever needs it and see how it works. this is the ecm diagram. let me know your email. will see what happens.

 

Mike,
Really good info. I may just reconsider. I'll send a reply to your email too.

Thanks.

 

The CCM is the master.
It controls the communications on the serial link.

These are the computers on the serial link:
1) CCM -- master
2) ECM -- slave, but can run vehicle standalone after security check at startup.
3) ASR/ABS computer -- slave
4) C68 climate control -- slave/optional
(As an added note, the C68 climate control communcates with the Programmer over a dedicated separate serial link that is not the same as the one mentioned above)

A good check is to disconnect the ASR/ABS and C68 climate control to see if the problem exists without them -- just disconnect the connectors from them.
This eliminates them from being able to load down the serial link.
The vehicle will run fine without them -- been there, done that.

The pre '94 ECM is notorious for problems -- it is under the hood with the engine heat.
The CCM normally doesn't have problems, but it does go bad.

At startup, the CCM checks the pellet resistance in the key and there is a encoded security handshake between the CCM and ECM over the serial link. After, that the ECM can run the engine standalone, but the "SYS" may come on.

The CCM requests data (vehicle speed, engine rpm, etc) from the ECM.
If the ECM doesn't respond, the CCM requests the info a few more times before deciding to set a serial communications failure code and displaying the SYS.

I don't think a quad driver will cause the problems you are seeing between the CCM and ECM, but it is possibly another indication that the ECM is the component to look at.

If your problem is serial communications link problems, I am betting the ECM is defective.

Tom Piper

 

I've got the factory service manuals for the 92. Let me know if you want to take a look at them.

 

Thanks all for all the good advice so far....I know I am going to get this nailed down.

I have some more clues from this weekend. I made my longest drive yet in my car since I got it and have discovered that this whole problem is intermittent. A couple of times this weekend as I was driving the whole thing was working fine but then would fail again. I was hoping to pull codes from it when it was working but it was not when I got home.

Also the CCM does not register that the door lock switches work and so the power locks don't work.

 

I don't think the "Communications Failure" on the ECM/CCM serial link will store as a "history" trouble-code.

I had a very similar problem with my '92.
I only saw the serial communications failure when I had my Vetronix Tech-1A scan-tool on and was monitoring it in real time -- that is when the SYS would start to flash in the speedo display area.
That code would not set to retrieve at a later time.

My problem was intermittent too; it only happened after the engine warmed up. That is what made me start to think about the ECM being under the hood with the heat of the engine.
My symptoms were:
1) Real-time "communications link failure" that would not set as a code to detect later.
2) SYS flashing.
3) ASR trouble code (this one would set for later retrieval) and trouble light
4) The C68 climate control green LED would flash but not store any codes.



Another thing to keep in mind, the CCM is much more sensitive to a low voltage condition than the ECM.
When my battery is low, I can start the car but I may get false CCM trouble codes and the SYS from a low battery condition.
If you think about this, the battery has enough power to start the vehicle but not power the CCM properly -- which I found interesting.
However, with the low battery problem, I get the SYS flashing immediately after starting the vehicle not at some time later like the ECM problem I had.

Tom Piper

 

P.S.

Since your problem is intermittent, good scan-tools (like the Vetronix Tech-1A, MasterTech, and Tech2) can take a "snapshot" of the problem (monitoring the CCM not the ECM) when it is happening to graph and analyze at a later time.

I never saw a single ECM trouble code the entire time, and the ECM was definitely my problem.

Tom Piper

 

Does anyone have a 92 ECM or CCM that I could try swapping out for troubleshooting?

 

Another thing to keep in mind is the CCM is programmed for your particular vehicle.
It has the odometer reading, the ignition key pellet information, the VIN # of the vehicle, and the option content programmed in.
So, your key pellet will probably not be correct for a "loaner" CCM and the vehicle will not start.
And, if you borrow a CCM from a vehicle that does not have the C68 climate control option or ASR/ABS (although, I think ASR/ABS are standard) and your vehicle does, the CCM is not aware that you have them, and it may not communicate with them.
However, without the C68 or ASR/ABS functioning you would still be able to prove what was wrong.

If you get a new or factory refurbished CCM, you have 100 miles to program it properly with your odometer reading, VIN, and option content -- after 100 miles, you are locked out and can't program it.
This is done to prevent odometer tampering.
Plus, there aren't very many scan-tools that have the software to program the CCM -- The Vetronix Tech-1A, MasterTech, and I think the Tech2 can do it. But, I don't think EASE or the others will.
At one time, even Vetronix would supply the CCM programming software to a dealer or delco shop only.
Look for CCM on this page:
http://www.vetronix.com/diagnostics/...st/bdy_gm.html

If I were you, I would put my effort into getting a ECM to prevent all the headaches listed above.

Tom Piper

 

I suspect that my CCM has been replaced. Carfax showed a odometer discrepency before I bought the car and I have a solid security light after I turn the ignition on. I have no problems starting the car but I will be troubleshooting the security system issues when I get my hands on those schematics. Right now I am guessing that the security feature has been bypassed or tampered with in some way.

 

If the CCM has been replaced from another vehicle, a good scan-tool with the appropriate software will be able to read the VIN of the vehicle the CCM came out of.
If the VIN is not the same as your vehicle, it has been replaced.

If the replacement CCM was new or refurbished, it could have been programmed properly with your VIN and option content.
A Delco Refurbished CCM can usually be identified by it having the case bead-blasted -- it will not shine.

Tom Piper

 

My '92 does the same thing. Why do you think the TPS is faulty? I checked mine and got .5 volts all the way to the EBCM.

I don't have the C68. I disconnected the EBCM cable behind the driver's seat and according to the FSM the Service ASR/ABS and Check ASR/ABS lights should have all been lit. All 4 lights didn't come on with the cable disconnected. Obviously my ASR/ABS didn't work but when those systems randomly go out they usually store codes (H41 in the CCM and H71 on the EBCM) and sometimes the electronic dash will go out for a few seconds and the radio will go out briefly at the same time. With the EBCM cable disconnected the dash flicker and radio flicker still occured. The SYS has only flashed 1 time and I think that was right before the cell collapsed in my battery. There have been plenty of times when the ASR/ABS won't work when I start the car. When that happens I get an ERR on the EBCM and I can't even access the codes on the EBCM. Since the CCM and the ECM suffer a data comm loss and the EBCM just stops responding sometimes, I don't know which if any of them is causing the problem.

I've read on other threads that the ECM can't be purchased new now and that there have been many people who have had to buy several ECMs in order to find a good working unit. Could the PROM on the ECM cause a failure? Mine has a Hypertech chip installed by a previous owner.

I don't mean to hijack this thread but I've been running into these similar problems for 6 months now.

Thanks,
Dave

 

The dealership had to fill out a card with a description of the failure for the people that were to refurbish a defective ECM.
That way, for an intermittent problem, the factory technicians at least knew what to look for.

I don't think many of the after-market companies to that.
When they put it on a test fixture and don't see a problem in a set amount of time, they simply put it on the shelf for the next customer -- intermittent problem and all.

Tom Piper