Stephonovich

A couple weeks ago, I came out to the car after it had sat for a couple hours, and it wouldn't start - it cranked, but no starting. My first thought was the immobilizer, so I pulled the key out, checked the key for cleanliness (it's my understanding the lock cylinder reads the resistance of the key - yes/no?), and tried again. Still no go. Checked all fuses and relays, nothing. After about 10 minutes of off-and-on trying, checking, and cursing, it magically started. The problem didn't surface again until a few days later. In all cases, the green key icon on the dash has turned off. I believe this means the immobilizer has been successfully disabled.

I read up, and found that a weak battery can be the cause. Mine was aged somewhat; the car especially didn't like cranking when the temperature dropped below 40 F or so. So, new battery - starts faster, but alas, the problem still occasionally happened.

On one instance, I pulled the backup (ECU, right?) fuse for a few minutes, put it back in, and voila. No idea if that was the cause, or a coincidence.

I tried pulling the key off the ring, as I read that sometimes other keys or dangly metal bits in the vicinity of it can cause this problem. Once again, it worked once, but not every time.

My spark plugs were replaced with NGK Laser Platinums at around 65K, so they should be fine. Additionally, the car has zero engine issues when running.

I've read the cam position sensor can cause a refusal to start, but if that was going bad, wouldn't it run terribly, too?

It's also worth noting I have a Viper alarm, with an immobilizer. A good car electronics shop installed it; not me, not Best Buy. I know, I know... "Probably that, figure it out." What kills me is that I've had it installed for a year, no issues. It just started, and again, is seemingly random.

I have another key that I had cut awhile ago which I'm going to try driving with for awhile, to see if that fixes anything. Any other thoughts, opinions, or threads I missed would be appreciated.

HS2K007

Look for the wires under the dash were they connected the alarm. I know you stated they were a good company, but check how they connected. If you find wire taps.....not a good company. Why? The wire taps only cut into the wire insulation and tend to work loose over time and cause shorting of the electrical system. This can cause the "sometimes it works, sometimes it does not". Most companies now, even the good ones use these crappy taps since they are faster, they do not pay enough to keep good installers and the customers that already paid $400 for the alarm do not want to pay $$ to have it put it by a good installer.

If you look at the wire connections and they are soldered. This is a good installer, but it does not mean that solder is done correctly. If the solder did not weld the wires together well, it could be coming loose and causing shorts. The connections will be taped or heat shrink, so you will not be able to tell unless you unwrap them.

Not saying this is the issue, but most cases a good starting point since you have checked the other areas. When the car will not start, just try to move some of the alarm wires. If it starts after doing that, you have a short in one of the starter disable wires.

If you find wire taps... Bring it back to the shop that did the work and have them solder connections before the car catches fire.

Billman250

Start taking note of the green key light each time you start the car.

When you turn the key on, it should go on, then off.

If it's flashing while trying to start, or just flashing with the key on, then you have an immobilizer problem.

If it's cranking, and the green key light is off, then the immobilizer is not the problem.

Cam sensors would set an immediate CEL and store a code.

Right off the bat I'm thinking alarm.

Stephonovich

To the install... yes, there's wire taps. I noticed that a few months ago when installing my hard-wired 12V for the Valentine One. (I did not, in fact, use a wire tap) I would take it back, except they're probably pissed at me due to having them special-order a head unit and never having it installed due to a sudden financial crisis depleting my fun money. I can solder them myself.

One interesting note: I had a second key made before DFR '13, and started using that about three weeks ago. Since then, I've had zero problems. The other key was OEM, came with the car. Can a key transponder go bad only some of the time?