I have a 1992 Vette, LT1, AT, car runs great, but at times the dash display will flash "sys", using a GM Tech 1 scan tool, it will freeze when this happens, the data stream freezes, i.e. checking eng coolant temp it will stay constant and not increase although it should. Once "sys" stops flashing, data stream continues, temp is now correct, etc. Car continues to run, so ECM is functioning, NO check eng lamp when eng is running, so NO hard faults. Code 41 is stored, loss of ECM data stream. Is the ECM failing at times or is Mem-Cal at fault? Also, Check ASR lamp is on at times, could relate to ECM issue. Any help would be appreciated!! Thanks.

 

Check your battery first. Mine was doing this when I first got it and it was a bad battery. The low voltage messes with the ecm. It is very common.

 

Here, you need this:

http://forums.corvetteforum.com/c4-t...n-96-cars.html

 

Hi, thanks for the info!! The battery voltage is low 12.1 volts, eng off and it should be at least 12.6-12.8. I will try another batt and see if that helps. But charging voltage is OK, over 14 volts. My last Vette '91, had too many electrical problems and I sold it. The '92 has very few options, base car and the LT1 is a much better motor. Only had 60% throttle, scan tool, and after fixing that the car really moves. Thanks again for the help!!

 

Before you go throwing money at the problem, you might not need a new battery. There is some resistance between the battery terminals and the point where the dash measures your voltage, so the digital readout is not an accurate way of reading voltage while the car is off.

A better way to check your battery would be to use a multimeter and probe from one terminal to the other to check for voltage while the car is off (key not in ignition, everything electrical turned off, no current being drawn out of the battery at all). 12.0 or less means dead, 12.1-12.9 approximates how much it's charged depending on where in that continuum it lies, and 13.0+ is overcharged.

Read your CCM codes like I suggested in my previous post and tell us which one you've got (Edit: your year might not have those diagnostic features, actually. If not, just try to find out which codes are being thrown by all modules; you got a code 41 from the engine computer, but what codes are the rest of the modules throwing? Your EBTCM definitely has a code stored because of the ASR error.) Reading all the codes that are there is much more logical than simply guessing what they are and throwing money at a new battery. I very strongly doubt your battery has anything to do with the fact that codes are being thrown; it could be anything.

 

Check the battery connections to make sure they are tight and free from dirt. I had SYS flash on my dash a few years ago after I took it out of storage. It turns out the negative cable was loose. I tightened it up and the problem went away.

 

The Tech 1 scan tool has shown codes 025, 41, 054. While reading the service manuals, it mentions the ASR issue and these codes are related. I have extra batteries, (lots of cars & trucks) to try. I purchased the car recently and installed a MSD Billet vented Opti-Spark, new water pump, it was leaking, power pullies. The car had issues with the "sys" flashing and the eng not starting or stalling when I bought it. Even after the new parts it would not start at times and stall after starting. But, now it seems to start OK and runs much better, 100% full throttle helps!! I can change the batt and see if that helps, very easy to do. Vette's are unlike many GM cars, I used to work at a Oldsmobile/GMC dealer (mechanic) and also as a fleet service mechanic with the City. City vehicles were mostly large trucks, but we did have the Electric S-10 pickup, much like the EV-1. The Tech 1 & 2 scan tool was very helpful and the only way to check out the Electric S-10. This was many years ago and I have since retired. The dealership work was '79-'85, then it was the City. I hate just replacing parts, but don't know enough about the Corvette systems and oftentimes, it's a very simple fix to a odd problem. So, I'm not a newbie to cars, but the Vette is so different to me and how they fit all those parts in such a small place?? I will never know. GMC Generals are HUGE, but a lot easier to work on, LOL. Thanks again for all the help!!!

 

Update on "sys" flash. Pos batt cable had lots of corrosion, 2 ohms between batt cable and main harness junction box (behind) batt. Cleaned cables and it helped, but still flashes "sys" at times. DVOM on batt shows 12.4 to 14.5 VDC eng running, AC on, cooling fan running. May be problem with alternator or battery, should maintain system (less voltage drop) One reply stated 13 VDC is overcharging, not sure why this answer was given. GM vehicles will see 14.1 -14.6 VDC when charging correctly. I will use a battery charger to keep batt up, eng running, 14 VDC or so, and see if that helps stop "sys" flash. Not sure "sys" flash has so much to do with batt voltage, dash display did show same as DVOM when checking gauges. It was in incorrect before. But , it is getting better and I appreciate the help!!!

 

The problem with "sys" flash continued after the repair to corroded batt cable. Pos cable had a lot of corrosion. Charging voltage seemed down at low RPM with accessories on. Took alternator apart and found debri had damaged one brush, cut grooves in rotor slip ring, causing low output. Cleaned up the damage, tested everything, reassemble, install and it now charges as it should. 14.7 VDC at idle, "sys" flash is now gone as is check ASR light. Batt is good, alternator was the problem, it was charging at higher RPM's, but not enough output at idle. Thanks for taking me the right direction!!

 

I'm pretty sure that he meant >13 Vdc when the car is off and you're checking it with a DVM indicates an overcharged battery.