@Grimace@1985corvette refer to posts #'s 2 & 13 that @IHBD wrote. It answers you question about key codes whic, as i undersntad it, has to do with what the key's ohm (resistance) reading is. To check your key's ohm value, you need a multimeter. You key sjhold have a little chip on each side of the metal part next to the plastic part. Set your multimeter on a figure that looks somewhat like the letter "r" and take the multi's leads and touch each lead to each chip, and the multi will show your ohm value.

 

1985 do not have VATS.

 

Follow up to sending the ECM from my '94 LT1 to Keith at PCMFORLESS. I mailed it last Friday. Keith received it yesterday, Wednesday afternoon, and called me. We discussed my LT1 is stock, no mods, burning 91 octane. He deleted the VATS. Lowered the temps the fans turn on to 195/204 to run with a 180' thermostat. This combination will let the engine run at an optimal temperature for the best fuel efficiency. He set the timing for 91 octane fuel. He programmed the shifting so it will be quicker and smoother. Keith said this programming will let the engine produce 20 more horsepower. Keith returned the ECM via UPS late Wednesday afternoon. UPS tracking says i will receive the ECM tomorrow, Friday. end of day. I will report back once i have the ECM installed and have drove the car. We have thunderstorms Saturday and Sunday. Depending on what time i receive the ECM from UPS, and get it installed, it may be possible to go for a test drive Friday. I am very much looking forward to having my LT1 running again, no threat of VATS acting up and how the performance changes. I will follow up.

 

are you sure it’s a 85 ? No vats in 85

 

Interestingly, I just had a VATS issue over the weekend, and it had me fooled for a bit, as I wasn't paying attention to the SECURITY light, and also didn't know about the 3 minute reset.

Saturday AM turn key... everything lights up but no start.... Maybe a low battery? Get jumper pack, and connect... starts right up! Let idle to charge the battery. Stop for gas, restart, no issue. Several more stop and start throughout the day with no issue.
Sunday AM, off to a car show.... no start! Now I have the jumper pack handy and connect it, but still no start... After futzing with it for a while I give up and go inside for a bit , was staying over at my brother's so wait for him to get up, then go to show him what was happening... and it starts right up!

Get to the show, no problems. Judging comes around and ask me to start the car... no start! I didn't bring my jump pack with me, but brother had one in his car so he went to get it... hook it up to my car and it starts right up!

Show ends, car starts right up. Get to my brother's house unload some stuff then get ready to leave and... no start! Connect jumper pack, and still no start.

Now we bring out the multimeter and start probing around and there's no voltage drop or anything when key turned to start. My friend finally observes that the security light is on solid, and asks if that's correct.
So I check the owner's manual... and read that after a failed start, the system won't reset for 3 minutes... so all the no-starts I had the couple of times the jump pack worked were when it wasn't convenient... it took more than 3 min to get it and the system reset... the times it didn't work, the jump pack was already in the car ready to go, so <3min system hadn't reset!

I take a closer look at the key... the VATS chip is shifted to one side and moves easily. With it pushed to one side, SECURITY light is on... I center it, and no SECURITY, and car starts right up.

What a frustration, but mystery solved!

So now I'm considering one of the bypass things, but not sure where it gets installed...

 

The more experienced minds can jump in here, but... In my reading, the "bypass" aka "resistor," module, etc is a bandaid attempt to prevent the problem inevitably happening again. The chip on the key is only one of three parts to VATS, the remaining two parts of VATS can also malfunction, leading to the problem recurring again. The permanent solution is to have VATS deleted from the ECM.

 

Go to a key shop and get a new key. The shop near my house charges $20 for a GM VATS key. Enjoy your car. Don't try to fix things that aren't broken. A functioning VATS system does provide a layer of protection against drive-off theft.

The biggest take-away from this episode should be that you now understand the interaction with a VATS event, the SECURITY light, and the timer interval. Get a new key. My bet is that you never again have another VATS related inhibit for the remainder of your ownership of the car.

 

Well I have 3 keys....
Funny thing is the one that failed was the newest one, and was a GM blank, that I just got last October. But yes I will probably get another replacement now

 

This for sure seems like a legitimate solution for @mackguy or perhaps he already has a 'spare' that he needs to rotate to daily service. If the resistance is known the fabrication of a 'plug & play' of correct resistance to just carry maybe. His experience also reinforces the need to carry your mechanical code and also resistance with you when traveling.

 

Yes, I will just retire the faulty key and get another replacement, though having this happen makes me also want to carry a backup solution, so I am trying to figure out the easiest way to do that.

 

Measure the resistance in the pellet. Use the chart earlier in this thread to determine your VATS code and write it down where you know you can find it if you need it. Make up a bypass resistor of the required value and carry it in a discrete location in the car. If the wires on the key cyl fail (the other likely failure point) you can install the resistor to get you going again. Knowing the mechanical code for the key is also helpful if you loose the keys, but having several available negates this requirement, IMO.

I had trouble with my 90 VATS. It left me stranded 150 miles from home. I got a ride back with another member on the tour and retrieved the car with my truck and trailer. Like yourself, I wasn't yet super familiar with the system. (I did however know what the solid-ON SECURITY light meant.) It turns out that my "bypass resistor" had a cold solder joint in it. Once I sorted out my self-inflicted issues, I had no further trouble.

My current 1992 has a functioning VATS system. I carry the resistor. I'm not concerned at all because I understand the system. Most of the "problems" peeps have are because they don't understand the system. Other than the key, the wires on the key cyl, and the contacts, the system is reliable. CCMs don't cause trouble.

One risk of reprogramming the ECM is that it can get lost or damaged in shipping. Then what?

 

Yeah, I have the resistance value already I'm just not sure where the bypass gets installed...

 

In your FSM see 8A-201-10 Fig 29 for the C281 connector. That's the wires from the steering column cylinder and ideally you put a correct resistor into an older scrapped connector from a lock cylinder so that you can insert if needed at that point.

 

Very dependent maybe on the capabilities of the programmer there's likely much more than just loss/damage to be concerned about!