HELP!!!! Truck wont start..

I have a 1998 crew cab 454 automatic.
Now when I go to turn the truck on it acts like it wants to start and then it cuts off right away.
I pulled the codes and they are P1631 and B2960
which are security codes one is anti theft and the other is invalid key.
I clear the codes and its as if they were never cleared cause it keeps doing it.
I am using the original key so...
I had an alarm and disconected that thinkin that it would fix it but the problem has come back.
It will come and go it hasnt done this in about a month and it started doing this about 2-3 months ago. i changed nothing around that time so idk..

Can anyone help me?
this really sucks....

Thanks
Robert

Had this problem with an 02 Tahoe. Try plugging in the factory stereo and see if that solves it. We discovered this after blowing the intake tube off with half a can of ether.........

The only thing I can think of...

Was it just an alarm or remote start alarm? If some had put a r/s on it, then maybe the bypass module is bad or the wire that you tap into isn't a good connection?? I have had this issue when doing remote starts when the bypass goes bad, but I never get check engine lights though either.

Just a big shot in the dark

yeah I had asked them about a bypass when I went over there they said my truck didnt need a bypass. so there isnt one apparently.
Yeah it is a remote start though.
thanks though

and i dont think i will have any luck the factory stereo.... dont have one and dont know anyone that does

So I did a search the b2960 one and found some info that said that you have to just turn the key on but not the truck. wait a few secs and then turn the truck on. it seemed to work as of now. im not sure if it was a coincidence or not. the code for the p1631 is still on and no matter what i do i cant seem to reset it. and the security light is still on so idk what the heck is going on.

So if there is anything else that anyone can think of let me know.

Thanks
Robert

My 99 and my 2000 both have/had bypass modules. I would imagine the 98's need it too. You can search online to find if there is one for it. Try directed's site or bulldog security or call crutchfield they will know for sure.

Alighty i will check into it.

Thanks

Passlock on these trucks began in '98. If the security light comes on flashing, then it's activated and that's what shut off your engine immediately after it starts. If it comes on and stays on, it's indicating a fault in the Passlock system but should still allow the truck to start.

Remote start setups on these trucks do require a bypass module to work correctly.

There are a lot of problems with Passlock once the truck gets some age on it. The typical problems are bad tumbler, bad connection at tumbler, bad connection at body control module (BCM), or steering column/ignition tumbler or BCM replaced without matching the two pieces or doing a security relearn.

Some people think the key has a "chip" in it like the old VATS keys that you could see the resistor, but it is not true; the '98-up Passlock system key is a normal key just like '97-down. On Passlock the "chip" is in the tumbler.

The body control module (BCM) is the black box with bright green harness socket, sits behind the dash a little bit above the driver's side of the transmission hump. The BCM also contains the theft deterrent module (TDM) which is what the resistor in the tumbler is in circuit with. Usually the BCM won't bone you unless you replaced the steering column or tumbler. When I do a column swap in these trucks, I try to get the BCM from the donor truck, but I'd only do this if the trucks were very similar - I'm not totally familiar with what all other functions the BCM provides.

I've heard, but don't know for fact, Passlock can be tuned out of the PCM - so if you're thinking about getting a custom tune, you should ask about it. It's really a problematic system that is difficult to get right once it starts failing, usually because the fault can be intermittent for a long time before complete failure.

Even with a bypass setup, you are still having to communicate with the BCM so if it or the connections are faulty, you haven't solved the problem with the bypass. The typical bypass unit takes over for the resistor in the tumbler to allow remote start without the tumbler being turned.

To sum up:
Normal operation: security light on steady before starting engine (bulb check), turns off after start.
Security activated: security light flashing after start, engine dies immediately after starting.
Security failed/bypassed: security light stays on steady after starting.

By the way, all the above symptoms are my conclusions based on direct experience with several of these trucks, combined with service info about this rotten system.

Sorry for the novel, just wanted to share as much info as I could on this because it can be a PITA to find answers.

Richard

Man that is some great info. Thanks I appreciate it.
So here is what happens as of right now the light stays on continuously and I am able to start the truck but it will stay like that for a while and then like you said when the light starts to flash the truck wont start.

So you are sayig it could be anyone of the BCM problems- tumbler, sensors, connections, and or the actual module?
But even if those are replaced it still might not solve the problem?

And I mean if the "tune" thing works Id give it a shot but I am pretty much trying to leave it "stock" you know.

Also if there is not a bypaas in the truck then its not like its going to matter if i put one because it still has to communicate with the BCM anyways?
Which could be the problem?

Sorry if I repeated your explanations back to you I just want to get a better understanding.

And I really appreciate you postin up.

Thanks
Robert

I wonder if there was a bypass in it at one time, well there had to be for the r/s to work. IF someone had removed and the reference wire has been spliced together, that connection could be bad. It will be a set of tiny wires that run down the column from the tumbler, down under the dash some where. It has been a few years since I have done a r/s so I can't remember colors or # of wires. Yellow is what comes to mind.

I seem to remember a wire in the column a loooooonnnnnng time ago that might have been cut I will check that.

Thanks
Robert