cadillacderek

YES... THANK YOU VERY VERY MUCH FOR THE LINK...LOTS OF GREAT INFO THERE... i read the entire thing word for word and i think i may be on to something as a result!!... i went out and connected pin A to pin G and the it threw 2 codes... C12 (on board diagnostics opperational)...and H46 (VATS ERROR)... pretty much what i expected..
i went to module 1.4 ( Cycle CCM Output Status) it tested a bunch of different relays and i could hear them all clicking except for the courtsy light relay, even though the lights were on?? so im gonna track that relay down and replace it and hope for the best... its a long shot but its somewhere to start looking
another weird thing is after pulling the codes i removed my "1 off Kustom made ALDL jumper apperatuss" lol (basicly a bent up a kotter pin), i started the car and everything was normal... i let it run to see if the LCD would go black again and sure enough it did after idling for 4 or 5 minuts, taking the interior lights out with it again.. so i shut the car off and tried pulling the codes again and nothing showed up on the LCD?? im wondering if the CCM has a bad connection or bad ground? i'll try and locate it to check... will post progress soon ... THANKS AGAIN FOR THE HELP GUYS

chevylu

Diagnosing a problem from afar is usually an exercise in futility, but you seem motivated so if you’re game I’ll give it a go. I believe this sentence is the key to your problem: “I used a Autoxray scanner and it came up- theft code.” If this sentence is accurate, you have a VATS problem. What you need to do is verify what Autoxray is telling you by using your Corvette’s built-in diagnostic system to (1) retrieve the code that is set, (2) refer to the Factory Service Manual description of that code and (3) follow the diagnostic chart to pinpoint and fix the problem. It’s that simple (and that complicated – sigh . . .). Your 1990 Corvette has three separate and distinct diagnostic systems: (1) DERM, (2) ECM, and (3) CCM. Page numbers below refer to the 1990 Factory Service Manual (FSM).

Pg 9J-2 DERM Diagnostic Energy Reserve Module
Monitors Supplemental Inflatable Restraint system ( SIR)
If the DERM detects a problem, it illuminates both the INFL REST and the Fasten Seat Belt indicators
Pg 9J-5 Picture of DERM
Pg 9J-A-2 DERM Codes
Pg 9J-A-3 Ground teminal K (A=ground / K=SIR diagnostic terminal

Pg 6E-2 ECM Electronic Control Module
Monitors emission controls, fuel delivery ignition, idle air flow, fuel pump
If the ECM detects a problem, it illuminates the Service Engine Soon indicator
Pg 6E-6 Ground terminal B (A-ground / B=ECM diagnostic terminal
Pg 6E3-A-1 ECM Codes Also on page 8D-8

Pg 8D-2 CCM Central Control Module
Monitors driver information switches and displays
If the CCM detects a problem, nothing is illuminated
Pg 8D-4 Ground terminal G (A=ground / G=CCM diagnostic terminal)
Pg 8D-5 CCM Codes
CCM is module 1 and and ECM is module 4

You don’t need a scanner such as Autoxray to diagnose a ’90 Corvette. You just need to learn how to use the Driver Information Center (DIC) to show you diagnostic codes (Pg 8D-2). In brief you do this by clicking on CCM Diagnostic Codes at http://wagtail.home.att.net/extras/ . Print the pdf document. While you’re at it, click on VATS Bypass and print that too (I wrote both documents to complement one another). Read both documents and try to retrieve the codes.

If you do this, here is what I think will happen: Your good friend DIC will report a code such as 51 (VATS Invalid Key Detection). If you have the full FSM, Code 51 will be on page 8D-48 where you will find information on how to resolve the issue. In a nutshell, here is how you fix Code 51: (1) Make sure the key has a good, clean pellet of the proper resistance; (2) Make sure the ignition switch contacts that interface with the pellet are clean and in good condition; (3) Check for other poor connections. If this doesn’t fix the problem, most folks end up either replacing the ignition switch module or installing a VATS Bypass. IMHO the C4 VATS system is a poor design ameliorated by a bypass. Other VATS related codes that you may see include CCM codes 52, 53, 54, 61, 62, 63, 64, 65, and ECM Code 46.

For additional info, click on Search. Click on Click for Advanced Search. Enter VATS for the Keyword. Leave Search Titles Only as is. Under Search in Forums(s), Click C4 Tech/Performance. Click the Search Now button. You ought to get around 195 results split into 8 pages. Read some; the more you read, the broader your knowledge base. I’d bet the answer to your issue is in there somewhere. Good Luck.

chevylu

Do you have a FSM?

Code 46 is on page 6E3-A-58: "Code 46 will set if the proper signal is not being received on CKT 229 by the ECM when the ignition is turned on."

Be careful. Don't jump to conclusions.

For extra credit read this: zamm.home.att.net/zamm/zamm.pdf
Use zamm/arete

cadillacderek

Chevylu,.. thanks for your detailed replys, and patience with us new guys!! it has helped alot!!
I dont have a FSM yet... but i just bought 2 manuals off ebay... one is a 1990 service manual and the other is a section 8A electrical diagnosis service manual supplement.... i figured it couldnt hurt to have both? so now its the hurry up and wait game untill they get here.
here they are, hopefully there the right ones??

http://cgi.ebay.com/ebaymotors/ws/eB...B:EOIBSA:MT:31

chevylu

Everyone here gets to be a new guy; unfortunately we all get to be old guys too . . . but that's another story.

Congrats on your buy. Unless you're independently wealthy and you don't mind getting to know your personal mechanic a little too intimately, I think you'll find $94.50 to be the best investment you make this year. On the other hand, now you have to read the thing and learn how to translate gm-speak into English.

Read this article http://www.motor.com/article.asp?article_ID=668 and learn to love the diagnostic charts in your manual. Try to get over any tendency you may have to throw parts at a problem; you’ll save money in the long run and teach yourself how to think. Print a copy of the L-98 Engine Start Sequence by grumpyvette here: http://forums.corvetteforum.com/c4-t...post1544028429.

Finally, as you work through this problem and all the problems to come, try and remember this sage advice: "Assembly of Japanese bicycle require great peace of mind."

cadillacderek

thats a good write up on the start sequence... i'll print that now!! and i1ll read the other link when i get back tonight and have more time.

meanwhile i have a question for you since im still waitin for my FSM to actually get into it, im trying really hard not to jump to conclutions but its still driing me crazy today i remembered that i have an autoxray scanner and i figured i would try and scan it while the speedo LCD was black to see if it would give me something new or whatever... well anyway when i scanned it and it said "vehicle not responding"... my question is do you think the VATS system could cause this??

chevylu

I don't think it is "directly" related to the VATS system. It sounds like you may have an intermittent ground problem. Take a look at:

http://www.batee.com/corvette/dcrg/index.shtml

and

http://www.batee.com/corvette/dcrg/r...den/index.html

and

http://www.corvettemagazine.com/1999...ash/dashp1.asp



Note the 1984-1989 C4 Instrument Cluster Issues

mike o

MR. CHEVYLU I think I love you!!!!! You have givin me the best info and ideas so far. Derek I now know your in the loop and getting this info as well so I'm sure that very soon we can, and will solve this problem. Also I'm convinced that you may be more on it than I am, so that encourages me and motivates me as well, THANK YOU !!! I will be trying and checking into many things this weekend. I will stay in touch and let you know what I find. I swear our problem is so much alike its killing me. THANK YOU FELLAS

cadillacderek

its killin me too!!!

i was just digging around on the forum and came accross a thread i think you should read... (link below) please read it all the way through... it starts out sounding like it may be an expensive fix but ends up being a simple ground
i know that the cars they have are LT1 cars... meaning the lights flashing on their dashes are probably different then ours... (among other things?)... but alot of their other symptoms seem very simmilar?
what im wondering is if the CCM for a L98 is grounded in the same spot on the block?? or close??
im gonna check tomorrow, ill let you know what i find

READ HERE:

http://forums.corvetteforum.com/c4-s...cm-or-ccm.html

Thanks

chevylu

That is an excellent thread; I printed a PDF copy for future reference. Thanks! Incidentally, if you like to capture any information you run across to a computer file, take a look at doPDF http://www.dopdf.com/.

When your FSM arrives, take a look at page 8A-14-4 in the Electrical Supplement for information concerning Ground Distribution. Look at page 8A-203-0 to identify the physical location of the grounds. By the way, as you become familiar with your FSM, make sure you pay attention to whether you are looking at information pertaining to the L98 VIN8 or the LT5 VINJ.

Back in ’91, a year after I got my Corvette, I was introduced to our good friend DIC because of a ground-related issue. This thread http://forums.corvetteforum.com/c4-tech-performance/2313136-inflatable-restraint-light-1990-c4.html captures some of my frustration. Take a look at FSM Index on http://wagtail.home.att.net/extras/ for a list of other frustrations over the past 19 years. Each one of those rows translates into time, effort, and money. Are you sure you want to own an antique?

My headlights were the latest thing to require attention (see the headlight repair sticky at the top of the forum page). Fortunately, this time around, the fix required time and effort, no money. I rolled my own (bushings that is - on my lathe).

gw962

Mike, I had the same sort of problems with my 90 last year. Mine turned out to be dirty connections to the CCM. It would not read the correct A/D count shown in the CCM diagnostics.

After correcting that, I'd still have an intermittent "no security" light such as you describe. I'm assuming that it is because of corrosion in the switch, but if I remember to put a drop of oil on my door key every month and work both lock mechanisms, I have no problems. You might try that and see if it helps.

mike o

I will try oiling my key tommorrow, and it seems to make sense. How did you determine the bad connection on your CCM? I have had mine out and it seemed fine, I freshend up the grounds and put it back in. Have you had any problems with your LCD, dash lights, or interior lights? I'll let you know if WE ever solve this, THANKS.

cadillacderek

hey everyone...
i found 6 wires that grounded on the lower bell housing bolt on the driver side they were dirty so i cleaned the crap off them and it didn't help a thing, so i took my cluster out to check the connector plug to that and it looks good too.
still waiting for my FSM so i can do actuall diagnosis

hey gw962... was the connection to your CCM visably dirty? could you see corrotion or?? i think im gonna pull the CCM today and check for problems there on my car, hopefully ill have good news to report soon, Thanks for your reply, any help or opinions are appreciated!!!

gw962

I pulled the connections since I was getting an incorrect VATS A/D count. I tried some contact cleaner first and it solved the problem.
Knock on wood, I haven't had the issue since the fix.
I've been lucky enough to not have any LCD or dash light problems. Maybe because I followed another writeup on removing the dash unit and checking and cleaning the main connector and LCD connections. I'm not sure if you've tried this, but even though time consuming, it appears to do the trick.
Good luck with this. Believe me, I feel your pain having fought the problem for 6 weeks and 2 tows.

gw962

I was doing a quick check, before yanking the CCM, and kind of crammed under the dash to get to the connections. I couldn't really see except to spray the contact cleaner. Once I plugged them back in, I got lucky and it's worked since.

edit: The FSM shows two grounds for the CCM, both going to G106 which is on the side of the block, just above your oil filter. G107 grounds to the bell housing, so you may have cleaned the wrong one.

chevylu

Fellas: With respect to the CCM ground, take a look at CCM Issues at Avoiding the Tow Truck. This just might help solve your problem.

cadillacderek

GREAT INFO ON THE AVOID THE TOW TRUCK SITE!!!
yesterday i pulled ground G106 off the side of the block, above the oil filter and ONLY 1 wire was grounded there, it was the big one that comes directly from the battery, thats it!! no little wires at all?... the pictures on the avoid the tow truck site show 2 or 3 small wires going to that ground.. where did mine go??
when i cleaned the grounds that went to the lower bell housing bolt there was 5 little wires that came out of the harness AND the braided line that went to the frame, (total of 6 connectors grounded) how many should be there??.
should i take some wires off the bell housing stud and put them back on G106?? if so which ones?

hmmm.... actually, now that i think about it, G106 is a much bigger bolt so im thinking only the ones that are supposed to be there will fit?? i think i'll try that tomorrow
THANKS AGAIN GUYS!!!

tim32920

I had the same problems before .Go to http://www.vatssucks.com/ it will help you out tremendously and you can bypass the whole thing and not have to worry about it again.

cadillacderek

grounds are clean and in the correct locations now and it still freaks out.... im leaning towards the CCM itself being bad?? i got my FSM today so im gonna check that next.

will report back soon

chevylu

Take a close look at Chart #1 on page 8A-50-8 of the Electrical Supplement.

There are four simple tests that have binary (yes/no) answers.

According to the chart, the problem is the CCM itself ONLY if the answer to all four tests is yes (test light on) and the CCM connectors are OK.

If the answer to one of the questions is no (test light off), the problem is not in the CCM; it is an open, a short, or a fuse in an associated circuit.

Your diagnosis is complicated by the fact that your problem is intermittant and you need to run these tests when the CCM appears inoperative. When the CCM seems to be functioning, work your way through Chart #2 on page 8A-50-9.

Patience: Spend 20% of your time doing, 80% thinking.

Good advice from R.M.P: What you have to do is slow down—you’re going to have to slow down anyway whether you want to or not—but slow down deliberately and go over ground that you’ve been over before to see if the things you thought were important were really important and to . . . well . . . just stare at the machine. There’s nothing wrong with that. Just live with it for a while. Watch it the way you watch a line when fishing and before long, as sure as you live, you’ll get a little nibble, a little fact asking in a timid, humble way if you’re interested in it. That’s the way the world keeps on happening. Be interested in it.

~