1994 VATS bypass for CCM
12-20-2014, 05:22 PM
#1
Advanced
Thread Starter
Member Since: Mar 2009
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
1994 VATS bypass for CCM
I have searched for hours, The prior owner has already put the bypass resistors in the harness for the key, Intermittiantly the car will not crank. If I jump the starter interrupt relay it will start and die. I ordered a bypass online. It is a 30/50 hz generator. I believe I need the 50 hz signal. Problem is where iin the world is the fuel enable ckt. On Mitchell and the factory wireing diagram it does not show ckt 2229 a normally dk blue wire on pin #25 of the pcms red connector, heck its not even in the harness. All I can find is ckt 800 on pin d29 and d30 which is a tan wire- I am not sure this is it. Can anyone shed some light on this.
12-22-2014, 08:31 PM
#2
Melting Slicks
Member Since: Aug 1999
Location: Baltimore, MD USA
Posts: 2,240
Likes: 0
Received 34 Likes
on
30 Posts
I have searched for hours, The prior owner has already put the bypass resistors in the harness for the key, Intermittiantly the car will not crank. If I jump the starter interrupt relay it will start and die. I ordered a bypass online. It is a 30/50 hz generator. I believe I need the 50 hz signal. Problem is where iin the world is the fuel enable ckt. On Mitchell and the factory wireing diagram it does not show ckt 2229 a normally dk blue wire on pin #25 of the pcms red connector, heck its not even in the harness. All I can find is ckt 800 on pin d29 and d30 which is a tan wire- I am not sure this is it. Can anyone shed some light on this.
When you turn the key to start, the relay closes and 12 volts passes thru the relay to the starter solenoid Purple wire. The solenoid energizes and 12 volts goes to the starter motor.
The CCM also sends a signal to the PCM via the serial bus to enable the pulsing of the fuel injectors. If the hand shaking doesn't take place the fuel injectors will be disabled which is why when you bypass the starter enable relay the engine only runs for a second.
As far as I know pin 25 was only used on the F body cars which had a separate module that provided the signal you mention. You could try hooking up that module to pin 25 and see if it works. Other wise you could have the EEprom programmed to disable VAT's.
That signal only enables the pulsing of the fuel injectors and will not cause the no crank problem.
I do know someone that has used a PCM out of a F body in a Corvette and programmed with the corvette firmware with VAT's disabled and it worked. My conclusion is the PCM's must be functionally the same but in the Corvette schematic pin 25 is not labeled as being used and on the F body it is.
On the diagnostic connector ground pin 4 to pin 12 and see if any codes are set. A CCM DTC 54 is FEDS fuel enable failure but even with that error the starter should still crank.
12-22-2014, 10:28 PM
#3
Advanced
Thread Starter
Member Since: Mar 2009
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
c4 vats issue
When you turn the ignition On, the CCM reads the key pellet and if the value matches the resistance the CCM was programmed for it grounds the Yellow/Black wire at the primary coil of the theft deterrent relay.
When you turn the key to start, the relay closes and 12 volts passes thru the relay to the starter solenoid Purple wire. The solenoid energizes and 12 volts goes to the starter motor.
The CCM also sends a signal to the PCM via the serial bus to enable the pulsing of the fuel injectors. If the hand shaking doesn't take place the fuel injectors will be disabled which is why when you bypass the starter enable relay the engine only runs for a second.
As far as I know pin 25 was only used on the F body cars which had a separate module that provided the signal you mention. You could try hooking up that module to pin 25 and see if it works. Other wise you could have the EEprom programmed to disable VAT's.
That signal only enables the pulsing of the fuel injectors and will not cause the no crank problem.
I do know someone that has used a PCM out of a F body in a Corvette and programmed with the corvette firmware with VAT's disabled and it worked. My conclusion is the PCM's must be functionally the same but in the Corvette schematic pin 25 is not labeled as being used and on the F body it is.
On the diagnostic connector ground pin 4 to pin 12 and see if any codes are set. A CCM DTC 54 is FEDS fuel enable failure but even with that error the starter should still crank.
When you turn the key to start, the relay closes and 12 volts passes thru the relay to the starter solenoid Purple wire. The solenoid energizes and 12 volts goes to the starter motor.
The CCM also sends a signal to the PCM via the serial bus to enable the pulsing of the fuel injectors. If the hand shaking doesn't take place the fuel injectors will be disabled which is why when you bypass the starter enable relay the engine only runs for a second.
As far as I know pin 25 was only used on the F body cars which had a separate module that provided the signal you mention. You could try hooking up that module to pin 25 and see if it works. Other wise you could have the EEprom programmed to disable VAT's.
That signal only enables the pulsing of the fuel injectors and will not cause the no crank problem.
I do know someone that has used a PCM out of a F body in a Corvette and programmed with the corvette firmware with VAT's disabled and it worked. My conclusion is the PCM's must be functionally the same but in the Corvette schematic pin 25 is not labeled as being used and on the F body it is.
On the diagnostic connector ground pin 4 to pin 12 and see if any codes are set. A CCM DTC 54 is FEDS fuel enable failure but even with that error the starter should still crank.
12-22-2014, 11:22 PM
#4
Melting Slicks
Member Since: Aug 1999
Location: Baltimore, MD USA
Posts: 2,240
Likes: 0
Received 34 Likes
on
30 Posts
Awesome dude. Thanks for the help, I know the key/pellet is bypassed prior to me getting the car. I am sure now that the bypass i got will not work for this car, I tried something today- stuck the key in the door and unlocked it- car fired right up. Hmmm I thought passkey and VATS were seperate in this 94 vette. Anyhow any recommendations on someone or software to reprogram the vats out and maybe get a few more HP? Merry CHRISTmas.
The factory alarm part of the system only pulses the horn. It's turned off by using the door key. It does not prevent the starter from cranking. Only the Pass key part of the system disables the starter and pulsing of the injectors.
As for reprogramming the PCM, http://www.tunercat.com has a software and cable package for around $180.00.
Click on LT1 tuner kits. You need the 94-95 LT1 Kit.
I think a tuner would charge you around $75.00 or more plus shipping.
When you have the no crank problem is the Security light off? If it's on, it indicates the key pellet bypass resistor wasn't read correctly and a CCM code should set.
As for more horsepower, buy a C5,C6 or C7.
Last edited by Hooked on Vettes; 12-22-2014 at 11:59 PM.