bypass VATS with out key 96 vette LT4

[dave69]

I would like to start my donor 96 vette LT4 before I pull the engine out and swap it into my 69 pick up. I don't have the ign. key. I looked at the shbox site and all I found was how to bypass VATS with a resistor you need the key to do this. There must be an easy away to do this. Can any one help. Thanks

[6772owner]

I only know of the resistor mod or having the VATS programmed out of the PCM, I dont think there is an easy way, the point was to make it harder to steal the car. You could just have the VATS removed from the PCM, you're going to have to have it done for the truck anyway....

[LockDoc]

No easy way to do this unless the key code is on a sticker in the glove box. Some are.

LockDoc

[brn agn]

Weren't there only 7 or so different resistors used? You could buy each one and try them until it works.

...wait a minute, we are not helping you steal a donor car, are we? Ha

[storm9c1]

The VATS system is nice to keep once you figure out the correct resistor value. Later you can put a switch in to cut in/out that resistor as a security device. Nice thing about having that switch is that once the car is running, you can bump it and it won't shut the vehicle off (unlike a conventional kill switch). It only reads the resistor at start up once.

Also, any 1994-1996 Chevy Caprice 9C1 (police package L99 or LT1) car with have a VATS system that is in "dummy" mode. Meaning it will send the correct signal to the PCM without needing a resistor. It was cheaper for GM to do that (include the VATS reader on the car but never program it on the 9C1 cars which do not use the special key). Civilian cars did come with the resistor key, so it must be a 9C1 (RPO code). What this means is that you can use a VATS module from a 9C1 Caprice and it shouldn't need the resistor.

When VATS is working (LT1/LT4), the engine will start for a few moments, then die. So you may be able to test your LT4, at least for a moment.

Otherwise you will need to figure out the correct resistor value in ohms. Here is a table. Note that you can come up with these values by using a potentiometer or resistors in parallel or series to get the right value.

KEY ID -- OHMS
1———— 0.402
2———— 0.523
3———— 0.681
4————-0.887
5————-1.130
6————-1.470
7————-1.870
8————-2.370
9————-3.010
10————3.740
11————4.750
12————6.040
13————7.500
14————9.530
15————11.801

[Todd Hepler]

Everything tom said is accurate - just note that the resitor values are in kilo-ohms:
1 -.402 is really 402 ohms
2 - .523 is 503 ohms

etc...

Also - using an incorrect value locks the vats system out for 10 minutes or so... potentially you could spend a couple of hours finding the right one.

I worked in a 12V install shop in the 90's installing stereos and remote starts - I can confirm that this is how the delay works.

another interesting option: http://www.fieroaddiction.com/passkey.html

Todd

[storm9c1]

Originally Posted by Todd Hepler

Everything tom said is accurate - just note
Also - using an incorrect value locks the vats system out for 10 minutes or so... potentially you could spend a couple of hours finding the right one.

I think you have some number of tries before it locks you out, but I'm not sure. And possibly disconnecting the battery will reset it rather than waiting for the timeout (I thought it was about 3-5 minutes). It's been a while since I messed with this stuff from a prior engine swap project, so your mileage may vary.

Oh, and if you are good with electronics, you can make your own dummy module with over the counter parts. http://home.hiwaay.net/~davida1/passkey.htm

[clinebarger]

Originally Posted by Todd Hepler

Everything tom said is accurate - just note that the resitor values are in kilo-ohms:
1 -.402 is really 402 ohms
2 - .523 is 503 ohms

etc...

Also - using an incorrect value locks the vats system out for 10 minutes or so... potentially you could spend a couple of hours finding the right one.

I worked in a 12V install shop in the 90's installing stereos and remote starts - I can confirm that this is how the delay works.

another interesting option: http://www.fieroaddiction.com/passkey.html

Todd

Originally Posted by storm9c1

I think you have some number of tries before it locks you out, but I'm not sure. And possibly disconnecting the battery will reset it rather than waiting for the timeout (I thought it was about 3-5 minutes). It's been a while since I messed with this stuff from a prior engine swap project, so your mileage may vary.

Oh, and if you are good with electronics, you can make your own dummy module with over the counter parts. http://home.hiwaay.net/~davida1/passkey.htm

Your ideas will work on F & B bodys. But the PASSLOCK system that Corvette uses is more advanced.

F & B bodys
The fuel enable circuit is an output from the theft deterrent module assembly and an input to the ECM. When the theft deterrent module assembly sees the proper resistance at the ignition key assembly, it will output a pulse width modulated (PWM) signal to the ECM. If the theft deterrent module assembly does not see the proper resistance at the ignition key assembly, it will not output the PWM signal to the ECM.

Corvette Y body
FUEL ENABLE DATA STREAM (FEDS)
The FEDS system operates in conjunction with the UTD and PASS-Key(R) systems. The FEDS system uses a password exchange system between the PCM and CCM after a correct PASS-Key(R) has been sampled to enable fuel delivery to the engine.

The password exchange uses the Serial Data Link (SDL) between the PCM and CCM. The PCM generated a password, scrambles it, and sends it to the CCM over the SDL. The CCM unscrambles the password and selects an appropriate response password. The CCM then scrambles the response password and sends it over SDL to the PCM. The PCM unscrambles the response password and compares it to the correct response it expects for the password it originally sent. If the response from the CCM was correct, fuel delivery is enables, and a message noting that FEDS has been successfully completed is sent to the CCM.

Originally Posted by dave69

I would like to start my donor 96 vette LT4 before I pull the engine out and swap it into my 69 pick up. I don't have the ign. key. I looked at the shbox site and all I found was how to bypass VATS with a resistor you need the key to do this. There must be an easy away to do this. Can any one help. Thanks

Have the VATS flashed out. The above post are great info but will not work on your Vette PCM.

[cparman]

I have a customer with an 85 Vette. there is no chip in the key? He says, do not leave the key in the switch or the car will not start for more than an hour. With the lateer model GM stuff, we will see security probs, and put a battery charger on them, leave the key on for an hour or so. the security system gives up and the cars will start. NOT SURE, but if you have access to a tech2, and you can go to the right page you might be able to turn off the RPO code for security??

Current Performance is a company in Hudson Fl, Jason is the owner. Might give him a call and see if he can reflash the PCM to bypass the security. He is a good guy

[dave69]

Thanks for all your comments I just finished putting together 15 different resistor combs to the corvette's key ID list I got them very close I heard you have to be with in 5% and I am so I will try it tomorrow before I pull it. I hope this will work.