Antitheft system

[rchurch5945]

OK - I had a headlight go out so I changed it out this morning. It worked a few minutes then went out again. I figured i just didn't snap the connection in good enough so instead of taking the headlight out again I removed the battery and horn and there was just enough room to get a few fingers in and make sure the connection was good.

But thats not the problem.

After reconnecting the battery the antitheft system kicked in. The engine will not start or even turn over. The parking lights flash. The little red light on the dash flashes.

I turned the key off for 30 seconds, then turned it to on. Left it on for 10+ minutes then turned the key off for 30 seconds. Repeated this process three times. Nothing.

Turned the key to start then to on, left it on 10+ minutes, turned it off for 30 seconds, repeated 3 times. Still nothing.

Put the battery on charge just to make sure it is fully charged, repeated on/off process, still nothing.

What am I missing? What am I doing wrong?

Thanks in advance for any help!

 

[wjburken]

OK - I had a headlight go out so I changed it out this morning. It worked a few minutes then went out again. I figured i just didn't snap the connection in good enough so instead of taking the headlight out again I removed the battery and horn and there was just enough room to get a few fingers in and make sure the connection was good.

But thats not the problem.

After reconnecting the battery the antitheft system kicked in. The engine will not start or even turn over. The parking lights flash. The little red light on the dash flashes.

I turned the key off for 30 seconds, then turned it to on. Left it on for 10+ minutes then turned the key off for 30 seconds. Repeated this process three times. Nothing.

Turned the key to start then to on, left it on 10+ minutes, turned it off for 30 seconds, repeated 3 times. Still nothing.

Put the battery on charge just to make sure it is fully charged, repeated on/off process, still nothing.

What am I missing? What am I doing wrong?

Thanks in advance for any help!

If I am not mistaken, some models of your vehicle have what is called Theft-Lock where if you disconnect your battery, you need to punch in a code through the radio.

Ideally you would have gotten the code from your vehicle prior to disconnecting your battery, but that’s not what it sounds like the case is. You will probably need to get a code from your dealer or from GM directly. You didn’t mention the make model or year of your vehicle so I’m just guessing. Here is a portion of the manual for my 1997 K1500 Chevy truck that discusses TheftLock.

 

[iamdub]

If I am not mistaken, some models of your vehicle have what is called Theft-Lock where if you disconnect your battery, you need to punch in a code through the radio.

Ideally you would have gotten the code from your vehicle prior to disconnecting your battery, but that’s not what it sounds like the case is. You will probably need to get a code from your dealer or from GM directly. You didn’t mention the make model or year of your vehicle so I’m just guessing. Here is a portion of the manual for my 1997 K1500 Chevy truck that discusses TheftLock.

View attachment 261960

That's just to prevent theft of the radio. Or, more accurately, use of the stolen radio once installed into another car. It doesn't lock down the whole vehicle.

Randall, do you have a key fob (keyless entry remote) for your truck?

 

[wjburken]

That's just to prevent theft of the radio. Or, more accurately, use of the stolen radio once installed into another car. It doesn't lock down the whole vehicle.

Randall, do you have a key fob (keyless entry remote) for your truck?

Thanks for the clarification on that.

 

[rchurch5945]

I'm sorry I didn't add the year - it's a 96 tahoe with the 5.7 vortec.

Yes I have a key fob but I've never used it. I probably will need to change the battery in it.

I've had this issue once before. When I was rebuilding the suspension and adding a lowering kit it sat in the shop for 6 months or so and the battery went dead. I charged the battery and went through the on/off procedure I described in my original post and it started right up.

I charged the battery overnight last night to just make sure it is fully charged and tried it again this morning - still nothing. This is getting really frustrating!

 

[Doubeleive]

If I am not mistaken, some models of your vehicle have what is called Theft-Lock where if you disconnect your battery, you need to punch in a code through the radio.

Ideally you would have gotten the code from your vehicle prior to disconnecting your battery, but that’s not what it sounds like the case is. You will probably need to get a code from your dealer or from GM directly. You didn’t mention the make model or year of your vehicle so I’m just guessing. Here is a portion of the manual for my 1997 K1500 Chevy truck that discusses TheftLock.

View attachment 261960

just giving you crap wade, lol

 

[Doubeleive]

I'm sorry I didn't add the year - it's a 96 tahoe with the 5.7 vortec.

Yes I have a key fob but I've never used it. I probably will need to change the battery in it.

I've had this issue once before. When I was rebuilding the suspension and adding a lowering kit it sat in the shop for 6 months or so and the battery went dead. I charged the battery and went through the on/off procedure I described in my original post and it started right up.

I charged the battery overnight last night to just make sure it is fully charged and tried it again this morning - still nothing. This is getting really frustrating!

Try disconnecting the battery again, while the cable is off go turn the key to run a couple times and press on the brake pedal a couple times, turn the headlight switch on and off a couple times, then go reconnect the battery and see if it starts.
the reason I say to do this is to clear any residual power out of the system, t could be from disconcerting the battery the first time that the power fluctuation caused the pass lock system to have an error.

 

[rchurch5945]

Chris - you mentioned a key fob. What should I try with it?

 

[iamdub]

Chris - you mentioned a key fob. What should I try with it?

I was just curious if it'd unlock the doors ("disarm" the "alarm"). In my mind, it's a way to visually and audibly ensure that the VATS (Vehicle Anti-Theft System) is disarmed, etc.

I like Doubeleive's idea with a thorough power cycle on it.

 

[rchurch5945]

After reading these posts I went out to the shop this morning, intent on doing everything that was suggested either in these posts or what I found on the internet.

I disconnected the battery, turned on the headlights, blinkers, etc to drain any residual power. Reconnected the battery and hooked up the charger to it to make sure it had a full charge.

My next step was to do the on/off sequence three times with the key. But first, I locked and unlocked the door with the key fob (the first time I've ever used it). Got in, turned the key and IT STARTED! Apparently the key fob will disable the antitheft system.

Thanks for all the suggestions and I learned a valuable lesson I really already knew: start with the simple things first!

In the past two days I have gone from I love my tahoe, to I'm going to shove it out into the highway in front of an 18 wheeler, to I'll sell it for $1 back to I love my tahoe!