corvette1987coupe

Has anyone had to replace the VATS module on a late C4?

From what I understand there is an Anti-Theft Module and a VATS Module.

The Anti-Theft Module controls doors open - alarm function, etc.

The VATS Module controls the fuel injection and starter enable functions, with a VATS Key communication.

The problem I am having more closely relates to the VATS Module control issues, on a 1992 coupe.

WW7

This should help ..thumbs:."Vats sucks" has lots of pictures.......WW

http://www.vatssucks.com/

WVZR-1

'92 does NOT have independent modules - the CCM controls all functions that were controlled by independent modules in '89 and earlier Corvettes. You can NOT use any of the same diagnostic procedures or assumed fixes when working on a '90+ with a CCM.

MrWillys

89 was the last year for the VATS module. Starting in 90 it was called the CCM. See here:

http://forums.corvetteforum.com/c4-g...dule-help.html

hooked073

If you would describe your problems I sure you can get pleanty of help on here

corvette1987coupe

[QUOTE=MrWillys;1586527313]89 was the last year for the VATS module. Starting in 90 it was called the CCM. See here:

The car will usually start after waiting quite a while. Then it will only start after the dash SECURITY light is flashing. It will not start without the SECURITY light flashing, which is usually the case in the beginning of an attempt to start the car. The starter circuit is locked out.

It seems to be having trouble reading the VATS Key, or something similar.

As a last resort I will try a VATS Bypass if the CCM is defective and causing this issue, but causing no other issues.
But if something more minor is the problem, I would like to correct that issue.

Can the ignition switch itself cause a VATS problem? If so, can the ignition switch be changed out without much of a problem involving the VATS system as far as additional cost, work, etc?

Thank you for the help.

MrWillys

3 Solutions:

#1 Program VATS out of the memcal, and bypass, and or ground starter enable relay.

#2 Get one of many resistor kits that replaces the key pellet read (probably the cheapest solution).

#3 Replace key switch with proper value resistance pellet in new key.

I believe the vatssucks.com site already linked will explain all of these options if I remember right.

WVZR-1

You mentioned "ignition switch" but I believe you meant the "keyed cylinder" and yes that is the most frequent cause of a problem and there are multiple reasons. If the tilt function of the column is used frequently then the wires to the cylinder are flexed very frequently. They're very light gauge and an issue. If your issue is sporadic I'd do this as the first bit of diagnosis and I would NOT try a new key first.

I would have the resistance of the key compared to the minimum and maximum values for that range. I would have a resistor of the correct value constructed and place it in the circuit under the dash at the connection to the column. If your "sporadic" problem disappears then you know that it's likely the "keyed cylinder" creating your issue.

You've spent very little time and very little money. Most any other "first attempt" will cost you much more.

Do you have multiple keys? Is the sporadic condition a regular occurrence with all keys?

1. and 3. in post #7 would be last resorts with 1. being the least desirable and 3. only after the diagnostic that I mentioned had proven that to be the issue.

Do you have small hand tools like a 1/4" metric sockets, metric nut-drivers etc?

Didn't you post something related to this car a few weeks ago? Maybe the GF's car? Looks and sounds familiar!

pcolt94

Can't add much to previous post it's pretty inclusive.

I have a cleaned the contacts (gently) on the lock cylinder for the VATS. If you look in there with a good flashlight you can see 2 copper contacts just about 1/4 " in. If you take a wooden Q-tip with alcohol you can clean them (wood Q-tips are thinner than the bathroom type and have a long stick for good visibility.

I would clean the key pellet. Measure the resistance with a digital meter and compare it to the mid range resistance for that key code .

WW7

I would try the above, then if that still doesn't work, go to the Ecklers Corvette site and buy a "Vats bypass harness", or you can build your own.... .Dealerships want anywhere from $350.00 to $500.00 to replace a lock cylinder, unless you can do it yourself then it will just be about $80.00 for the Vats lock cylinder...There are a ton of threads on here with people that have had vats problems. Vats does "SUCK",and it's a big pain in the azz for anyone having problems with it.. Eckler's even has a Vats bypass that has a switch on it, in case your worried about someone stealing your car without Vats hooked up....You can just throw the switch and no one can start your car..You can also use WVZR-1s idea and make your own harness, it's cheaper, but for non electrical people like myself it's easier to just buy one already made for $27.00...You do have to know your Vats resistance number, it will be between ( 1-15) so you'll need a digital meter to read your key....Personally , I think the engineers that developed Vats should be executed..( Just my opinion).........WW

corvette1987coupe

I just measured the Ohm value on both the keys the seller gave to me.
One key showed a lot of wear on it. The other key looked brand new.

Both keys had a Resister Value in OHMS of 1870, which corresponds to a VATS Code 7.

From what I have heard, GM had Briggs & Stratton design a security key system, and VATS is what B&S came up with.

WVZR-1

If you've 1870 then the keys check to be "design spec" and if everything were optimal you should have no issues. You mention "sporadic" so the substitution of a resistor in the under column harness would certainly be the least expensive diagnostics.

You could remove the hush panel, unplug the connector at the lower column and using your meter check the value registered at the lower terminals. If that value isn't consistently the 1870 spec and strays to maybe 1795 and less OR 1965 and more (what I'd expect) then you've confirmed your issue. You could try it several times positioning the column differently up/down when checking.

If you find an error in the reference resistance at the column base and elected to do a "keyed cylinder" replacement your present two keys would become "junk" and you would need two new keys done in the proper resistance BUT cut to match the code of the new replacement cylinder.

pcolt94

Back in 2012 I replaced my lock cylinder. Lots of cylinders to choose from on EBay and most are the same and just fine. I paid under $30 for the cylinder but I did have to buy keys (3) and get them cut. Think the whole deal was about $100 for everything.

WVZR-1 gave me a good link for disassembly of the column. Many have used it but I found out few months back it did not work anymore. Don’t know if there is a alternate source.
http://domesticmisfits.net/forums/viewtopic.php?t=124 (Does not work)


My link with some of my pointers when I did the cylinder.
http://forums.corvetteforum.com/c4-t...nder-94-a.html

Find the problem first, this would be last on my list.

corvette1987coupe

The above procedure is what I would really like to do next. I have hush panels removed on both sides of the car, as I have been trying to work on this problem ever since I bought the car a few weeks ago with this starting issue.

But before I start I want to make sure which connector I will need to unplug at the lower column, and the lower terminals. Are those lower terminals on that same connector I will be disconnecting? Is that a main steering column wire harness connector? Or is it one specific to the ignition key switch?

Sorry if the questions seem odd, but electrical troubleshooting is one of my weakness. I just want to make sure I am on the right track.
It's raining outside now and the car has a car cover on it, so I didn't get a chance to look under the steering column yet today.

Thank you for the help.

WVZR-1

Not a very good image but this is what you should be able to easily put your hands on:



You can do as you wish here to insert the resistor. If you're a "pick-a-part" type guy you can raid the salvage yard and just swipe a connector and do the cut/splice so you can plug it in without doing anything to your harness ends. I wouldn't cut/splice as the image mentions.

WW should have an old cylinder he might cannibalize the connector from and then you could just buy a resistor local and do a cut/splice/solder and - plug in!

corvette1987coupe

I will do this repair as soon as possible, as I would like eliminate VATS as a possible current or future problem

I have noticed that on my girlfriend's '92 C4, that as soon as I open the driver's door on her car, the SECURITY dash light flashes. Her car has no starting issue. This happens before the VATS Key is even put in the ignition switch. I believe this is the same case with my '95 C4, which is currently in storage, so I did not check it today.

As I have mentioned before, my '92 C4 will only start when the SECURITY dash light is flashing, and only when it is flashing. It only was flashing once early today and the starter attempted to turn over the motor, but the battery was too low to start it. I have charged the battery since then, but the SECURITY light has not flashed since that first time.

If working correctly, it seems like the SECURITY light should flash when I open up the door on my '92 C4, like it does on my girlfriend's '92 C4, even before I put the VATS Key in the ignition switch.

This is making me think it may not be the VATS Key issue, and maybe a Theft Deterrent System issue.

MrWillys

keep in mind that the BCM (body control module), and ECM (electronic control module) are different, but both authorized by the CCM (central command module). My point is that the door is BCM, and the key switch is an ECM, and starter enable relay issue. programming VATS out of the ECM's removable memcal, and bypassing, and or grounding the starter enable relay will remove VATS from the engine portion for starting.

corvette1987coupe

A couple of weeks ago I replaced the Starter Enable Relay, and I thought the problem was corrected. But the problem returned in a short amount of time. So it probably was not the fix.

It sounds like the BCM would control the flashing SECURITY dash light when I open the driver's door.

I just got the power door locks working for the first time. I replaced the blown power door lock fuse after I bought the car, but the second fuse blew after a short time. I replaced the driver's door actuator and put a third fuse in to get it working.

Cliff Harris

Here's a better picture of the VATS connector:



The small white wires in the orange sleeving are the ones that go to the contacts in the key cylinder, so those are the ones you use to measure the key pellet resistance.

If you're going to put in a bypass resistor(s), it goes in the other connector.

hcbph

If you buy one of the bypass modules, just unplug that connector and plug the bypass in place of the one with the white wires. No cutting and it's easy to return to original if you ever want to in the future.