VR'92

On my 92 one of these two computers is failing. Here are the symptoms:

1. The speedometer area (Digital gauge cluster) will completly go blank. It is still backlit while it is gone. It comes and goes as it pleases.

2. The milage still counts while it is gone.

3. Somtimes it flashes SYS but it hasn't done that in a while.

4. My datamaster setup will lose connection when the gauge fails.

5. The Cars tune suffers when it is failing.

6. Analog gauges still work.

7. Sometimes results in a no start condition. (I have VATS Disabled)

I have had tons of heat from my LT headers in the cabin somtimes. I think this has made the CCM get hot a time or too. I'm thinking it is the CCM but I really hope its not.

Which computer is failing? What can I do to fix this?

rubydog

When the ECM detects something wrong, it lights Service engine light. When the CCM detects something wrong, it displays "sys" in the odometer area for a few seconds. Run the ECM diagnostic by connecting pins a and b together on diagnostic under steering wheel. Count the flashes on check engine light. flash, pause, flash, flash is a 12 and is normal. Anything else is a code that you can look up.

Run the CCM test by connecting terminal g and a together. You will get codes displayed in speedometer area. The codes again can be looked up to see what was wrong.

I started with sys and security blinking, then check asr lit up. As long as this occurred after engine was running I was fine. But if sys and security light up when you turn on key (which it finally did in my case), you have a no start because the ECM and CCM are not talking on a serial link corectly. (No FEDS fuel enable...no injector turn over...fires and immediately dies).

I replaced ECM to no avail, mechanic replaced CCM. Still to no avail. I get CCM code C41 (and others) which means there is a serial link problem between these two gadets. My ruby (93) has been out of commission all summer because no one can fix it. The local chevy dealer (Radley) worked on it for 3 days and finally told me it was too old to fix, come and tow it home! Bummer. It is still at local mechanics place waiting for him to think about it some more! If you know of an expert in these things...please have him respond on this forum!

thanks...Rubydog

MickeW

Hi,
I also have the same problem with my -93, I have replaced the ECM, but still got this "service ASR light" comes up together with the "SYS blink" some times. So even I would be happy to hunt down this problem during the winter.

Regards MickeW

Check this solution http://www.digitalcorvettes.com/foru...threadid=35360

VR'92

thanks That will help with some trouble shooting.

corvette1989bham

Here is the solution: Guaranteed:
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PHONE CONSULTATION
After Gordon retired from GM's Corvette plant's Action Center, where he told GM's Tech Center and Dealers how to fix the Corvettes, he started For Your Car, Inc. to help the Corvette owners and shop technicians solve their troubleshooting problems by calling him on his consulting line 1-800-39-83883 (800-For Your VETTE). His fee is $10.00 per call, plus $3.00 per minute, while you talk with him. It is charged to your Visa or MC that you supply when you call. He wants to help you solve your problem ASAP and save you money

corvette1989bham

Did you ever get it fixed?

VR'92

Still working on it. Getting ready to try to replace the CCM but haven't figured out how to get it tuned. Really trying to avoid the local dealer if I can. I think I'd rather buy a Tech1a and try to do the CCM tuning myself.

Alvin

If you need a ECM to try I can send you one.. Just cover the shipping and a core charge.. If it works keep it.. if it doesn't than send it back and i'll refund the core charge.

VR'92

That would be great, Alvin. I'll send you a PM.

corvette90

hi

i had exact this problem when i burnt several chips...one burn was faulty, car ran in limp home mode, and SYS flashed....resulted in a code 51..

good luck

rubydog

I am having same problem with my 93. Mechanic installed new ECM and CCM. Ran fine for a month, now problem is back! Check asr, security, sys blinking. (If it does it upon turning on the key, engine will not start!) Have you any insight into this problem? Please help!

rick lambert

you can't do better than Gordon Killebrew-he's the man-and I'd bet he will cost a heckava lot less than the stealership!!!!!!!!!Also his
book on digi dashes with trouble shooting tech for $30. is worth it's weight in gold-well, maybe not gold-but it's like having the FSM that
the general didn't want you to have.

TOO_HOTTVETTE

I am having the identicle problem...SYS flashing, security and the service ASR. If the car is running when the lights start flashing, it's fine. Once I turn the car off, it will nor re-start. If i wait a while ( 10 min or more?) it will start. I just ordered an ECM..hoping that will cure this...Anybody have a solution for this????

rubydog

Hi, I have same problem. Mechanic replaced ECM and CCM. Worked OK for a month, then problem returned. Ran codes (ground pin lower left to upper right to run CCM test). Got C41, serial link down between ECM and CCM. This is identical to what I got before mechanic worked on it. If I wrap the new ECM with cold pack for hour, it will go away enough to start. Am thinking about getting another ECM, although this will be the third one! Any ideas would be appreciated. (I called that Gordon guy. he basically said that there a lot of bad remans (ECM) out there. Try another. Any ideas??

rubydog

93LT1

Since there's so many variations of the problem. Here's some information that I hope will assit with the resolution of the problem.

The CCM is considered the master, that is multiple devices such as the Electronic Brake & Traction ctl (EBTCM) and ECM devices all need to communicate to the CCM via the Serial Data Ckt.
Interesting is there's a password exchange between the ECM & CCM during startup attempt. If the exchange is not successful then there's a fuel enable issue. Car doesn’t start.

DTC41 is caused by the ECM not responding to the CCM signaling which needs to occur in a specific time period.

Physical layer focus:
The CCM has 2 Serial data ports ( E13 & F12) both ports terminate at a splice point as does all the other remote devices. The ECM connects via ports D4 & D15 and the EBTCM connects via port 4. All of these devices connect to this same splice point.

Again there's a splice that connects all of these devices which is the central point of the physical layer path. This splice is located behind the Cruise control module on the Instrument panel harness.
All the devices that connect to this serial Data link circuit all use the same color TAN wire.

I would triple check these links for shorts to ground and Battery and open circuits.
Keep in mind:
A short will take down the entire Serial data circuit, thus effecting communication between all devices.
A single open circuit will take down just that specific device.

So think of these links as a Hub and spoke. The splice is the hub and all the devices via TAN wire connect to this splice are the spokes.

Hank

Kryptonite

I have had a very similiar situation with my 93LT1 VERT, this car has been down since 10/09/2005, it has had 3 different shops to work on it, and now I am confident this shop will resolve my Issues.

1. Car has had several 4-5 ECMS installed work intermittenly and shut down.

2. CCM replaced to no avail.

3. Serial data loss

4. wiring harness issue.

At this point my mechanics says there is so much corrupted info between all 4 systems this car is severly confused. It sees different info everytime it goes into startup mode. He will have to reprogram several times in order for the car to recognize what it should do consistently. He has by passed all vats issues and currently has a key fob programmed and it works car didnt have a fob when I purchased it.

FEED BACK PLEASE Thanks KRYPTONITE

rubydog

What were your symptoms? "Check asr" lit up, "sys" & "security" blinking on dash? I am trying to find an ECM (not a reman) for mine to see if it resolves problem. I put a cold pack on my ECM (reman unit) and it will start, but within a minute, those lights start flashing. If they flash when you turn on the key (without coldpack), it will fire then immediately die. (FEDS fuel enable not getting to ECM due to serial link data not satisfied, so CCM does not send ECM fuel enable signal) Get various codes when running CCM test, among them C41. Do you know what codes your CCM test displays?
Rubydog

Kryptonite

All the syptoms you mention do happen I am not sure of the codes though My wrench tells me he close so I am still waiting.

VR'92

Update:

I have replaced the ECM. Hasn't helped a bit, So I'm thinking CCM.

I am getting the code 41. I have no money to troubleshoot right now.

Bradley1

I had a SYS flash on my 92 and it was a bad fuse in the box on the passenger side. I know it is simple but I would check all my fuses. As soon as I changed it out I had no problems. My AC and radio were acting up as well at the time. No problems since.