VATS Module?

I have an '88 convertable. We put a vats override on it a few years back because it would not turn over at all, that solved the problem. Over the last few months it has been getting harder and harder to start. It will turn over but won't start. I finally pulled the service manuals out and found out that the vats module behind the passenger dash will "disable" the fuel injectors. So I pulled the dash and found the possible offening part. Tested it per the service manual and the volts don't appear to be that off, I also checked the dark blue wire that runs from the vats module to the ecm and it does not show an open. When I unplugged the vats module and plugged it back in the car started fine, but I am not sure I want to trust it for long since it is such a PAIN to get to.

I searched the internet and called a couple of chevy dealers and parts dealers, and they all tell me that part has been discontinued. I have thought about junk yards but am afraid I might end up with the same problem I have now.

Can anyone help? Am I maybe looking at the wrong thing (although I really don't think so)? Is there someplace out there that sells vats modules? I can't believe that GM would discontinue a part that is required for a car to run - UGH!!

BTW I had the fuel pump replaced a couple of weeks ago because it died on the interstate, the starting problem existed before and after the fuel pump was replaces.

Thanks for any help!

I would more expect to have problems with the key reader. Very seldom see problems with the module.

Thanks for the feedback!! I am going to put the dash back together with the vats module "hanging" out so it will be easily accessable. I will also check for possible key reader problems. I would much perfer the problem to be with the key reader since there seems to be fixes for that

I guess the question I have is what kind of VATs override was installed a few years ago and how was it wired? A number of "overrides" involve running a wire to the starter which effectively bypasses the VATS for that signal. However, if the key reader was the original problem, the fuel injectors would also not work. Reconnecting the VATS to the cable might have addressed a loose connection issue which could explain why the bypass worked for a period of time.

I'm not a big fan of this system. That said, most of the problems I have seen with the system are with the key reader or the starter.

There is an excellent description of this system at: www.motorage.com/motorage/article/articleDetail.jsp?id=169809

The override is plugged into the connection on the wiring harness, not "hard wired". We disconnected the wires under the driver's side dash at the connector (did not touch the stearing column at all) and plugged in the override. It is the one like Ecklers sells if you search for "vats override". BTW highly recommended, it saved me these problems for 5 years or so.

When I pulled the override off while I was checking the voltage, it would not turn over at all, which is the reason I put it on in the first place. So, I wouldn't be too suprised if it is the key reader, but I don't want to start replacing things on a "might be" :)

The article you linked to is VERY INFORMATIVE and I will check it this weekend to see what I can find. Will let you know - THANKS!!!!

The VATS Override Cable is the right way to eliminate the key reader as an issue. It basically jumps the connector with the correct resistance to fool the VATS unit. No point worring about the key reader...... it won't help solve the new problem. I'm betting on a loose connection at the VATS unit which you have already addressed or a fuel pump issue (which is really suspect if it has not been replaced).

The fuel pump was replaced a week or two ago, so that should not be the problem.

I did not put this in my first post, but when it doesn't start (turns over but seems starved for gas) I do get a code 46 flashing, which is the vats code. That is why I took the dash to get to the vats in the first place :)

I am checking the voltage at the vats module itself (the dark blue for + and the black for -), and that seemed correct, even when it doesn't start. Is there someplace more reliable to check? The dark blue goes from the vats to the ecm, and is what the service manual says to check, but I didn't yet check the voltage at the ecm itself, just that the dark blue wire was not open. I guess the next check is the voltage at the ecm itself to make sure that connection is not loose.


Thanks for saving me the cost of a new key reader (at least for now) !!

I should have read your original post a little closer about the fuel pump replacement. Just so I have the sequence right:
1) Key reader not working, key reader bypass installed several years ago and has had no issue starting for several years
2) Recent problem appears that injectors are not energized at startup or fail at startup, ECM throws 46 error code.
Any other issues or major electrical problems?

The ECM is expecting a signal from the VATS unit which it does not receive which is generally why the error code is set. I would guess you have already checked the connectors on the ECM and there hasn't been any damage to the wires. The fact that it is intermittent led me more to consider the wiring than the VATS unit. However, you might be right that the VATS unit is/has failed. Your next question is how to bypass the VATS unit altogether and fool the ECM. That is a great question. I am sure there is a way and somebody has done it.

In regards to a salvage yard unit....the trick to that is to find a unit where the salvager still has the key for the ignition. By checking the key (ohm meter on the key "chip") , you will be able to order the correct VATS bypass cable to match it.

Let me know.

No other electrical problems, or any other problems (other than the fact that the darn thing won't stay started). Will crawl back under the dash tomorrow and check the voltage at the ecm to verify that that is working, and double check my readings at the vats itself.

The good news is that my husband found a new vats module (we think). I need to talk to them to make we are talking about the same part, I had called two other dealerships and they are the ones that told me it was discontinued, but then I am not sure they knew what I was asking for

Thanks for all your help Devo, I will post tomorrow with the results.

OK, rechecked everything this morning.

First we ran the two vats decoder module tests from the service manuals (decoder module disconnected) and all voltages and resistances were correct.

Then we went back to the ecm enable signal test. Test 1 (ignition switch in run) the dk blue to ground only gives 2.5 ish volts (the manual says it should be 5 volts). Test 2 ignition switch in start, the dk blue to ground gives 2.5 ish volts, which is correct. If test 1 doesn't give 5 volts it says to check the dk blue for an open, I did that and it is not open (0 ohms), so that is not the problem. The really screwy thing is that it sometimes started, sometimes not, while we were doing the test, even with the 2.5 ish volts on test 1. I did verify that when it didn't start it was throwing ecm code 46. So I am back to the vats module itself going bad.

Should I be checking anything else? or just replace the vats module (which is what I am leaning toward now)?

OK, looks like I am back to trying to find a vats module, junk yards, etc. The couple of places that showed them available on the internet didn't have any when I called this morning.

It would seem that is the best course to follow and probably the least expensive. Make sure that you get it from someone who understands what ignition key worked with it. Without the proper key, it will be a pain to figure it out.

Just so you know, I'm looking into another option for you which would be to replace the chip in the ECM. Some of my friends that race cars get the chip guys to turn off VATS for race cars where changing engines is commonplace. Unless you really want the VATS system (I can't imagine a single reason why) that would be the easiest way to solve this issue once and for all.

Check this out:

http://forums.corvetteforum.com/showthread.php?t=202488

I'm not sure you want to do the reprogramming yourself, so I'm still looking for a company you can buy a chip from or have yours reprogrammed. If anyone else can recommend a reliable service, please don't hesitate.

We found a "NEW genuine GM (General Motors) Factory Original Part" vats on e-bay. Only $75.00 and we were able to get it in the correct code, at least it is supposed to be the right one, I will see when it gets here.

I will definately read the information on reprogramming the ECM. I would rather keep the thieft deterrent, but if this one doesn't work, or breaks later, I don't want to have to go through all this again - UGH!!

Hope to have the new part sometime this week, and should know very soon after that if it works. Will update this and let you know, in the mean time if you find anything on the ECM reprogramming please post!!

Thanks again for all your help

Just got the new vats module in. Plugged it into the car and it starts!!! To verify that was the problem, I unplugged the new module and put the old one back in, no start for three tries. Plugged the new one back in and it starts first try.

Thanks for all the help, it is GREAT to have the car running again

Congratulations, I know that must have been a pain to deal with. I did find a chip company that custom burns C4 chips. Its name is MOTORVATION. They can turn off VATS at the ECM chip and eliminate the VATS module. It's not cheap $250-300, so you did the right thing.