Key fob not syncing with security system

Hey all

I have been battling this issue for some time now with no luck.

My key fob is detected by the car and can unlock it, but the push to start button does not send the signal to the actual starter. It won't even start if I hold it right next to the start button. This only happens after I have left home and am stranded in some parking lot somewhere. If I wait long enough (like overnight), or have the car towed to the mechanics, the car always starts and then works fine for a few days until the issue repeats.

The issue has never been reproducible at MY mechanics. In trying to solve the issue, we have replaced the starter, the relays, the car battery, and the key fob batteries. I have tried two different key fobs with no luck.

While on a road trip, I did get some insight into the problem. The car wouldn't start at the gas station (which also was a mechanics shop) after refueling. This particular mechanic came out to take a look for me.

1. He tried smacking the starter a bit to see if anything was "stuck" while I was trying to start the car
2. He verified the tail lights did work and that that wasn't confusing the security system.
3. He checked "the line that connects the push to start button to the starter" and said that when I push the start button, nothing gets communicated to the starter
4. He checked the new car battery and determined it was fine.
5. We checked the key fob, which is "detected" and works in that regard
6. Finally, if I understood him right, he bypassed the security system by connecting the car battery to the starter directly and jumped the car that way. He said that meant the structural components of the car are working fine and that the problem is likely a security clearance between the car and the key fob.

I can't find any information on this issue and I'm not taking this back to my mechanic (i think it is above his head). Also, I don't want to deal with this a bunch of times, going back and forth with the dealer.

I'm not a car guy, so I don't know if what I said even makes sense, it's just what I have been told. Any insight would be greatly appreciated.

Here is a link to what happens when I try and start it: https://youtu.be/0uXWACXm5TU

 

No aftermarket add ons?

When they truck acts up, will it let you lock the key inside the truck? That might give you a hint on the fob or button etc.

 

It sounds like you have messed with most everything but the antenna that is part of the PTS button. Might be worth a shot.

The other thing is that the free TechStream version in the 1st Post of the ECU Update thread can program keys / fobs. It might be worth deleting all existing programming there and reprogramming your keys? You would need a Tactrix adapter ($170). Do not use a cheap $20 version for this kind of programming. Also, a local might be willing to help you out for free. See my Feelers thread.

I do know that on the H key (physical key) side that if the immobilizer is not happy, the engine will crank but the fuel / ignition will not fire.

 

Also, you never noticed if the security light was on, on the dash?

 

Does your tpms light ever come on randomly?

 

I've never had an issue with Tire Pressure Monitoring. Nor have I ever noticed the security light being on either on the dash left of the steering wheel, or in the actual dashboard area.

One thing I forgot to mention is that when I push the start button, all the lights come on, the blower for air comes on, the radio comes on, just nothing with the engine

 

I'll have to check that out next time. Are you saying I should leave the 1st key fob in the car, and then use a 2nd key fob to try and lock the car?

The only after market add on that I know of is the Pedal Commander. I did not install it, the previous owner did

 

Brake light switch?

 

Yeah. Or touch the door handle. The truck shouldnt let you lock a fob in the truck and will make a loud beep.

 

Ahh, I knew I was forgetting something. My mechanic just replaced that 5 days ago and the problem occurred again today.

 

Unfortunately I'm not by my car anymore right now. I ubered home and waiting for my wife to get off work to take my back. Chances are it will start fine when I get back, but sometimes it takes 5 hours or so to... Reset?

 

I think there's two on our trucks. He replace the right one?

 

It could be a short related to engine heat, but that would be odd and really hard to find.

 

Do u think it's heat / temp related or time related?

 

If it were a heat based issue, wouldn't it occur more commonly after longer drives, and be safer with short-around town trips? It seems to have equal distribution, but I do a lot of short term trips i.e. grocery store around the block.

 

I feel like it's more time based because it occurs just as often with short trips as it does with long trips, but I'm really not engine knowledgable. Plus if it were heat based, wouldn't jump starting the car through the starter still have the same issue? I'm using the term jump starting, but it is not the traditional jump start where I hook up another battery to my battery and start the car. That does nothing. I think the right term may be hot wiring?

 

It depends. Around town, there would be more heat soak due to lower speeds. Still though, it would depend where the issue is at.

I'd still hit low hanging fruit before thinking harness.

 

Sorry, the reset I mean. Does the it seem to "reset" after a certain time? Or does it reset faster if it's cooler outside?

 

Not really. Like I said above, the immobilizer will allow the starter to spin, it just won't supply fuel or spark.

Supplying power straight to the starter, it will always spin but the engine will not start.

 

I don't really know if it resets faster when it's cooler. We usually just leave it some place and then come back several hours later.

The other night we went to lunch, after a 1.5 hour lunch it wouldn't start, so we ubered home. We went back to it just before we went out to dinner (which was like another hour later) and it still wouldn't start. We came back to it after dinner (another 2-3 hours) and it started and I drove it home. Thats when we took it back and have the brake light sensor replaced. I'm not sure if he replaced both. I'm going to have to call him