Viper 791 Key start

When you say it wo'nt start with Key...............Does it CRANK ?
Does your Security Light Flash??

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MO

Don't Learn from Others Mistakes
You Might Be the One That Knows.

A few possibilities:

1. As mo12v says, it's possible that the car is not recognizing your transponder key.

Remote-start the car and observe the red light atop the dash---it comes on solid for a second, then goes out. Now try to start it with the key----if the light is flashing, your key is defective or has become unprogrammed.

2. The Viper has a starter-kill feature which the installer probably DID hook up. If the alarm is armed, the car will not start.

The light does flash rapidlly when I turn the key(factory LED).  The blue viper LED does nothing.  It does it with both of my factory keys.  It does start with the key sometimes, but that is very rare.

Sounds like your keys have become un-programmed. When the factory security light blinks rapidly during crank it means that it is receiving an incorrect singal from the transpoder.  Unfortunatly without the 2 original factory keys (the ones that dont work) I have no idea how to program new ones.

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Other than the fact that it's a Ford, how could both keys get deprogramed?  Would it have anything to do with the bypass mod.

it could if the module were active without key sense hooked up... the vehicle would see conflicting or duplicate codes....

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

if it's a 556U or a 555U, then it's active all the time unless keysense is hooked up (dammned DEI.... why in the world would they do this???)

Try grounding the green wire on the 556/555U that they used in there and see if it solves the problem.

Gus


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Wherever I go, that is where I end up......

gus1]i wrote:

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it's a 556U or a 555U, then it's active all the time unless keysense is hooked up (dammned DEI.... why in the world would they do this???)

Try grounding the green wire on the 556/555U that they used in there and see if it solves the problem.

Gus

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Good Catch I forgot that if the security see's 2 keys it will lock the system up.

EDIT: Some cars when the security locks up the ignition it takes 15 min to clear, Not sure wich ones exactly but good rule of thumb is dont try it with any of them. Warn your customers not to show off their remote starters with their keys in the ignition.

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ISNT THAT WHAT I SAID??  ha ha

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

Why yes yes it is. lol

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I do have a 556U, but there is no green wire.  One harness has Red, Blue, Pink, Black, and Purple.  The other harness has a BLACK/ White, Black, and BLACK/ Red.  Which wire should I ground and should I just ground it straight to the chasis? Thanks for all the replies.

sopedish wrote:

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I do have a 556U, but there is no green wire.  One harness has Red, Blue, Pink, Black, and Purple.  The other harness has a BLACK/ White, Black, and BLACK/ Red.  Which wire should I ground and should I just ground it straight to the chasis? Thanks for all the replies.

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If you have a DEI 556U.........The harness with the wires you described should have a GREEN wire for Key sense, next to Purple wire.....
Check your instructions on it:

https://www.directechs.com/guides/manuals/ig/accessories/N556U_09-04.pdf

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MO

Don't Learn from Others Mistakes
You Might Be the One That Knows.

If you ground it straight to chassis, then the remote start won't work (interrupts the loop circuit). You could ground it out to chassis for testing purposes....

Keysense should be BLACK/ pink, if I remember correctly.

Gus


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Wherever I go, that is where I end up......

Key Sense is
BLACK / Light Green ( + ) or BLACK / Pink ( + )

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MO

Don't Learn from Others Mistakes
You Might Be the One That Knows.

I see where the green wire should be.  There's no wire there but there is a spot on the harness for it.  So what wire should I ground to what?  I'm thousands of miles from an authorized dealer and know only enough to be dangerous. 

Hmm. Before you rewire stuff, maybe experiment a little.

I am pretty sure it is true, as others here have said, that if the car sees two keys at the same time, it won't start.

I did not know that the 556U is active at all times if the keysense wire is not hooked up. That is odd. The more I think about it, the more I don't believe it----if it were true, the little relay inside would be on all night, and your battery would get drained. DEI does some unusual things, but not like that.

Anyway, as I was saying, experiment first. You want to verify if all your keys are still programmed to the car or not.

1. Unplug the 556U to temporarily eliminate it from the system.

2. Try to start the car with each of the keys you have, one at a time-------do the work now? If so, it's possible that the 556U is on all the time as others have said.

3. I know the remote starter works, but if you're particularly ambitious, remove the key that's in the 556U and try that in the ignition too. And you might even take one of your other keys, put that in the 556U, and try it that way too.



If the keys STILL don't work, then something is wrong with them or they have lost programming somehow.

But since you say they work sometimes, I think this is more likely to be an install-related problem.

Remember, for Fords, you need TWO working keys to program more. So if you still have two good keys, it's easy to fix-----if you have only one good key, you'll need a dealer or locksmith.

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A little about that 556U. I have just used a few of them when we ran out of our regular product-----they seem useful and versatile, but overly complicated too.

--About the keysense wire: The unit has two keysense wires; a positive and a negative.

Your Ford has a positive keysense wire (BLACK/ pink at the keyswitch or steering column), as mo said.

If you choose to connect the keysense feature (it can't hurt), read the instructions with the 556U and be sure you are using the positive keysense input.

The idea here is that when you insert a key, it disables the 556U, so the car can't see two keys at once.

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How do you have your 556U wired? Please describe what you have done with each of the wires. This is how it is supposed to go:

1. Red: constant, positive, 12 volts power.

2. Black: chassis ground.

3. Blue: when this wire receives a ground, the 556U turns on. It should be connected to either the blue or blue/black from the Viper remote starter------one is called "status", the other is "ignition 2". Either one of those wires puts out a ground when the remote starter is on.

(Since I do this professionally and speed is important, I simply jump the black and blue together, and connect them BOTH to the ground-when-running output from the remote start----yes, it is strong enough to power up the 556U-----but it is probably just as well if you connect the black directly to ground.)

For most installations, this is it for the 556U----all of the other wires would be shortened, taped up, and not used.

I like to just rip the unused wires out of the harness entirely, so the job looks neat, but that would make it difficult to hook up the wires later if needed.

the starter wire might have come undone on the key side.

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Eye am so re todd did.