2005 Ford F150 5.4 XLT. Viper model 160XV. I also have a DEI 556U immobilizer interface and a XCRS relay satellite box.
Intermittently key will start truck but other times only using the aftermarket remote start key fob will start it. When trying with the key if it won't start all kinds of stuff in the truck start clicking on and off. Some reason the flashers go on and off although the flasher lights on the dash never come on. Also never seems to make any sound that the starters trying to turn over when the key won't start it. But I can sit in the cab and lock all the doors and actuate the remote start fob and it will start right up like no issue. I can then turn the key on and the truck will run although the flashers keep flashing on and off for another minute or so. So I just bought the truck and I knew it had this issue so I don't have much history on it. Other than supposedly most of time it used to work just fine off the key and in fact I drove it home and it started quite a few times with the key. But now once again it seems the only start with the remote fob. The remote starter is an aftermarket add-on, so I'm thinking there could be some kind of wiring issue with it. Hoping maybe somebody's had experience with this in the past and can direct me on what to look for. Thanks!
Update 1: Forgot to mention the horn also goes off during this time I forgot I unhooked it cuz I got tired of hearing it. After realizing that it got me thinking this actually matches what happens when the panic alarm button is pressed not sure why that would be going off. Just putting the key in and turning on the ignition. Maybe this will help with the diagnosis.p
Update 2: so yesterday I decided to check the anti-theft light on top of my dash I noticed it flashes red all the time with the vehicles turned off . When I turn the key on, it goes solid red for second or two and then goes out. I'm assuming this means my Pats security system is working correctly. Truck is still not starting with the key However also observed that when I turn the key on and the flashers start going off and I suppose a horn would be honking but I have it disconnected that the buttons on my viper key fob will shut it off using the lock button. Maybe even the unlock button anyhow buttons on it work but the lock and unlocked on the factory Ford key fob does not seem to affect it at all. So I'm assuming that means that the viper alarm system is the one generating this panic alarm.
I finally figured out all the model numbers of my aftermarket alarm system it's a viper model 160XV. I also have a DEI 556U immobilizer interface and a XCRS relay satellite box. The good news is the immobilizer probably has another key that fits my truck as I only got one with it. So maybe now I have two. If I ever get the truck to start with just the key I can program another key. So my Hypothesis is right now that the remote starter box must somehow be interrupting the circuit to keep my starter from engaging. I know the starter wire has been cut to install the remote starter system, but I don't understand how it works fine with the remote but apparently it's not passing through the signal when not using the remote.
2005 f150