replace dei 555u/556u with 555c

I got a Viper 5900 that was installed in my 03 Ram 1500. I believe the tech (at Best Buy) installed it with either a DEI 555u or 556u module since I had to give up one of my spare key... In any case I don't feel too comfortable leaving the key (especially uncut) in the car. I ordered a 555C module which I'm planning on installing. From what I could find the only thing needed is 12V constant to red, output - signal blue to blue on the viper (I think, emailed DEI to confirm), then ground the gray wait to start during programming. Now the question is how the 555u or 556u are hooked up to the alarm? I couldn't find any wiring diagram for either module (not sure what the differences are between the 2). Any help would be appreciated.

FYI this only matters if you key rubber is gray, If the rubber is black then there is no chip in the key. The 555u is an older part the new one is a 556u they basically hook up the same. If this was done recently its propably a 556u there will be 3 wire hooked up red (12volts) black (ground) blue (Status out), and a black ring that wraps around the key cylinder. If is a 555u, there is only the red and the blue and the black ring.           just use the red and the blue thats all the wires on the 555c so cut out the wires on the 556u and remove the ring wraped aroung the key cylinder and use the wires (blue and red) that are already ran up to the 556u to hook up the 555c you need both the keys to program the 555c just follow the instructions to the T and you should have no problems programing it. some times it is a pain to mount the chip it has to be close to the cylinder so it might take a few tries just remember if you try to remote start the car and it shuts down quick,and then you try it again it might lock the car out so if you dont get it in a good spot on the first try start the truck with the key then try a new position for the chip on the cylinder.

excellent thanks for the info. Ya I have both keys and they are grey. The alarm was installed a couple of weeks ago so it might be the newer module. I guess I simple need to swap it with the 555c and find a good spot for the transponder. One more quick question... I've noticed that the remote requires two presses of the remote start button to start the truck... any way to change this or is this normal? I read something quickly in the install guide that mentioned it but doesn't say much else. Thanks again for the input.

2 presses is normal and the default setting.. it is a Safe Start feature so you dont accidentally start it by putting keys in your pocket, etc.... having said that,  the feature is programmable from one to three presses... (i have mine programmed for 1 press)Kevin Gerry

Certified Electronics Technician

MECP First Class Installer

Owner/Installer

Classic Car Audio

since 1979

Why go thru all that trouble? Just stick the key on a grinder and it won't work in the ignition. We have had a LOT of 556C issues and i don't trust them. The pellet can cause the RS to not work if it shifts even a little bit so secre it very well. You can even place the pellet in the 556U after programmed for very efficient usage. That way the ring is sending the signal...Mike M2

Tech Manager

CS Dealer Services

so put the entire 555C into the 555 or 556U or just the little tip? sounds ez enough, i'll just need to tap a couple of wires and just replace the key inside the module instead of having to run the new RF tip.

alright, i just spent an hour trying to get the 555c working but no luck. I tapped the 55c into the blue and red wire of the 556U. I then grounded the wait to start wire of the Viper 5900 alarm. I entered the programing mode using the 2 keys (I also programmed another key successfully so I know it works)... then hit the remote start button while holding the 555C receiver almost on the keyhole... no luck. I tried this several times... I even tried putting the transmitter inside the 556U and trying to program it this way... no luck. I actually hear the 555C relay click (I think it was coming from it when hitting the remote start key)... but it just won't take the code. I'm guessing I received a bad module... in the meaning I shaved the key and put it back in the 556U (still not too happy about that). I know someone posted that the 555C are a pain, just wondering how often they "go bad".

Have you grounded the wait-to-start wire on the 5900 when you're trying to program the 555c? C Renner's Auto Electronix

My service is cheap, quick, and good - pick any two

yup... the car does not start... wait to start is properly grounded... if I disconnect the ground while in learning phase the car will start right up but shuts down after a couple seconds since there is no chip present.

ok I gave up on the 555c, ended up getting a PKU-CH instead. Hopefully this will work out better, I'm still planning on doing what Mike suggested and place the antenna of the PKU-CH inside my already wired 556U. I was just wondering about the wiring for the PKU-CH. Red is supposed to go to constant 12V and brown to (-) Groundout from remote starter. I'm assuming this is the same two wire setup the 556U uses and I can tap directly into red and blue wires.