mgafun

Have Code 46 and No Crank. Everything else works. Need to get car to auto electrician's shop next week and want to avoid having it loaded onto a flatbed. Is there a way to bypass the VAT system this one time to get it running without destroying anything? Thanks.

CJWC4AZ

Did you try vatssucks.com. for info. Also, I'm pretty sure Gordon Killebrew had a way of bypassing. You would probably have to use the search function to locate that. Good luck.

redrose

what year ???????????????????

high possibilty that the problem is just at the ign key/resistor pellet/column wiring and a simple resistor bypass at the VATS module would work great, but later years of c4 get worse.

96vetteLT4

Great article in Corvette Enthuist this month about the vats and bypassing it. If you dont get it(definetly the best C4 mag.) go on line as they might have a link....G

gmc's88vette

PCMforless.com has vats bybass chip. Worked great for me.

mgafun

Sorry, 1988

rodj

But if it was working before I would be cleaning the contacts on the key and the column first.Do you have a 2nd key to try.
Measure the resistance of the key module and buy a resistor from Jaycar or Dick smithto do the bypass.

http://www.thirdgen.org/vats

mgafun

Thanks, I'll try that.

86PACER

Yes, simply provide the small terminal on the starter solenoid with battery voltage yourself, while the ignition key is in the "On" position, not crank position. This will get the car started and save you a visit with the flatbed. You have to repeat this each time you turn the car off, untill you fix the VATS problem. This happened to me, and this is how I made it home, then to the shop (before I turned my own wrenches) the next day.

The small starter solenoid terminal has a small purple wire. The VATS system is what allows or interupts battery voltage feed to this wire to engage the starter. Manually giving this small terminal battery voltage yourself with a jumper wire bypasses the VATS glitch, and starts the car so you can at least get it to your house or repair shop.

What I do is use a small piece of wire to bridge the large nut on the starter solenoid which is holding down the thick positive battery lead right next to it (always hot), to the small terminal that already has the single purple wire on it (VATS feed). This engages the starter and as long as you have the key in the "On" position inside, the car should fire up. A wire with a small aligator clip on each end will work perfect.

Be carefull not to touch your jumper wire against the engine block. Since I have a quick battery disconnect **** on mine, I first cut the power to the car. Then I can safely bridge the starter solenoid by feel. Once I have a good bridge and no short against the engine block, I restore battery power to the car with a turn of the **** and the stater begins to crank the car. Once the engine is running on it's own, I reach in there by hand and just quickly pull the jumper wire out.

rodj

As noted by people who know more than me

"the VATS module applies power to the starter solenoid as well as to the ECM's injector pulse enable circuit. You can crank the car all day with the starter enable bypassed but the car will never run without the ECM injector enable signal present"

" 86 + ECM puts out a 5v signal that must be go to "sink" (ground) at 30 Hz through the VATS module before fuel (injectors) is enabled and starter relay is tripped... if the ECM 5v signal is open/grounded at other than 30 Hz, NO GO...the starter relay can simply be bypassed (jumpered) but the ecm MUST either get that 30 Hz sink OR be re-programmed to eliminate VATS to pulse the injectors."

mgafun

Good stuff. Will try that tomorrow. I also have the quick battery disconnect switch.

86PACER

Definately worth a try. It's always worked for me.

I guess I should have asked first. Is youir car not cranking at all, or cranks but won't start?

mgafun

Both keys' resistance measures the same ohms. Will get equivalent resistor, but does it go between the two yellow wires coming from the ignition switch or in series with just one of them?

mgafun

Not cranking at all, throwing a Code 46. This after I was messing around down under trying to install another turn signal flasher closer to the driver so I could hear it better. Didn't work, created this instead.

86PACER

Ok, Code 46 means your ECM is not pulsing the injectors, because it's not seeing the signal from the VATS Decoder Module (pictured below) for what ever reason. Yet you mention the car won't even crank.

So my starter method should make the car crank, but technically should still not want to start due to lack of fuel.

You probably did something to the key cylinder wiring under the dash when you where under there. Did you leave it disconnected or disturbed the wiring? I'd double check the key cylinder wiring.

mgafun

Everything there seems as it was before I got in there, but I'll double check everything tomorrow.

engle1147

Sounds dumb I know, but have you worked both key locks to make sure the VATS isn't hung up doing its job. The horn works right?

I agree with the ohm the pellet thing...go to radio shack and buy some resistor for $3 hook them together in series until you get the same value as the pellet in the key then plug each end of the resistor string into the VATS connector at/under the steering column and try to crank her up again.

86PACER

Because a Code 46 combined with a no crank only has two possiblities, a bad VATS decoder module, or a problem with the key cylinder/wiring, topped with the fact that this started after he was messing around with the turn signal, I'd start with the key cylinder wiring.

It's a two wire connector on the steering column. Both wires coming from the key cylinder are black before the connector.

rodj

Goes between the 2 wires in the plug FROM the dash ; not the plug to the key.

redrose

AND the wires that go TO the key MUST be DISconnected from the circuit (potentially could have the key pellet become active again and total resistance of the pellet + "new" resistor would be half of reqd value - vats would shut down)