Security Light Issue - SOLVED

[SBellew]

Good morning. My 99 OBS Tahoe is driving me crazy. I have a solid Security light and she will start and run for 2 seconds. I have attempted the Passlock relearn, but the light does not go out after the 10 minutes. I have replaced the key cylinder and cylinder lock housing. I also got another module with the same GM part # from a salvage yard. The light refuses to turn off after the 10 minute period during the relearn procedure. I searched and could not find any info for when this happens and would appreciate any suggestions. Thanks in advance.

 

[Doubeleive]

Good morning. My 99 OBS Tahoe is driving me crazy. I have a solid Security light and she will start and run for 2 seconds. I have attempted the Passlock relearn, but the light does not go out after the 10 minutes. I have replaced the key cylinder and cylinder lock housing. I also got another module with the same GM part # from a salvage yard. The light refuses to turn off after the 10 minute period during the relearn procedure. I searched and could not find any info for when this happens and would appreciate any suggestions. Thanks in advance.

what about the key?

 

[SBellew]

The keys for the switch were included in the new set.

 

[east302]

Do you have a good scanner like a Tech2 or Snap-on? It’s almost certainly stored a few codes (B and sometimes a U prefix) and the GM manual has the diagnostic procedures for each.

You can download PDFs of most years at this site:

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

I don’t remember if they have 99 - go with 98 if that’s the case and it’s probably close enough if not the same. Volume 1, Section 9D has the Passlock info. A subscription to alldatadiy.com is another option and is exactly the same material as the GM manual.

One thing that the manual does mention repeatedly is to clear any Passlock codes before doing a relearn. It’s probably not nuclear-level-biohazard critical since many have successfully reprogrammed without clearing codes, but you may just be the unlucky exception.

If you don’t have a scanner, take a look at the code tables anyway. It’ll probably give you some ideas of things to check.

 

[SBellew]

It shows a P1626 DTC (Theft Deterrent Fuel Enable Signal Not Received).

I tried clearing it and doing the relearn and the Security light still did not go out after 10 minutes. It also shows that passlock is not equipped on a system scan.

Running a live scan during cranking, the VTD fuel disable goes to active, then back to inactive.

 

[exp500]

Sometimes, parts replacement is a problem. I think STRATTEC was OEM key. Fords in this time frame were a problem area.
Does your scanner have a program key function?

 

[SBellew]

Sometimes, parts replacement is a problem. I think STRATTEC was OEM key. Fords in this time frame were a problem area.
Does your scanner have a program key function?

From talking with a locksmith, the key in passlock 2 is not anything special in the system, only the lock cylinder, housing and passlock module. Same issue existed before anything was changed out. VATS and passlock 3 have special coded keys. My scanner sees no passlock module, not sure if that's a scanner or module issue. It's said not installed on both modules.

My scanner: https://www.amazon.com/dp/B09XV8VR35

 

[east302]

Here is the P1626 diagnostic from volume 3 of the manual. If it isn’t communicating with the Passlock module, then it’ll refer back to the Module diagnostics section which is Volume 1 (9D) of that link that I posted earlier. It’s too many pages to copy onto here, but it would be worth looking at.

One thing it does mention - see if fuse 4 (gauges) or 21 (sec/strg) is blown.

I guess it depends on if your scanner has the functions needed to get to the information mentioned in GM’s diagnostics. These things can be annoying, for sure.

You are correct about the key - there’s no chip in it and the Passlock stuff is contained within the steering column.

 

[SBellew]

Thank you. I downloaded the 4 volumes last night and am getting ready to start tracing wires. Long 3 day weekend will be perfect. Gotta build my dad's 4.2L in his F150 this weekend too.

 

[Eman85]

FWIW if you find someone that reprograms modules they can delete that POS system.

 

[east302]

FWIW if you find someone that reprograms modules they can delete that POS system.

A good point…might just be easier to ditch the Passlock and be done.

 

[SBellew]

True, trying to stay on the cheap side of things. Would love to get rid of it. Anyone on here have an ECU programmer?

Thought about trying this guy out: https://newrockies.com/
30 day guarantee, but $300, sheesh.

 

[exp500]

There are several threads on here about adding a resistor to the wiring. With a little thought and a little bit of investigating your voltages and timing, you may find the solution very inexpensive.If the timing part of your module has failed, then that should be replaced. Programming it out, as said above is another worthwhile and less expensive solution. Good Luck. https://tinyurl.com/Gm-link

 

[SBellew]

Thanks, I am ready to try anything honestly.

 

[Fless]

Not sure if this will help, but:

 

[Greg Simmons]

Not sure if this will help, but:

I had same problem with ‘99 Suburban. Spent 700 at a dealership only to have problem resurface a couple of weeks later. Took it back to dealership who had insisted it could not be programmed out and they kept it a week and said they couldn’t get it to repeat and said you owe us another diagnostic fee to which I told them to shove it. Reprogrammed by Blackbear deleting security and it’s worked fine ever since. 8 years ago and picked up 1 mpg, and truck runs smoother.

 

[ZKWBQD]

what about the key?

I feel your pain. I hate all of that automatic lighting stuff. On my new Tahoe, I've disabled all the automatic lighting and DRLs. Works just like my old 2000 Suburban now. I love it.

 

[SBellew]

So, doing doing more testing. I noticed that on B6, there is supposed to be a 5 volt reference. Mine is showing almost 0 voltage. Can anyone tell me where this reference voltage comes from do I can track down why it is not showing up? Or is that generated from the passlock module itself? I looked in my manuals and found circuit 705, but it only shows to the steering column connector and could not find where it went from that point.

 

[east302]

Is the EVO/Passlock module supposed to get the 5V reference from the Passlock sensor on 1836? It looks like it then uses that for the signal to the EVO sensor on 705.

For 1998, they show it in Volume 2 with the EVO/Passlock module.

 

[SBellew]

Found my problem. Security module I got from junkyard was also bad. Bought a third and it works like a charm now.