anti-theft chips ?

[Programmer]

Hey--test bench is no problem. Mine just happens to
have 4 discs and 8 firing pins.
If you can find that stuff--that'd be fantastic.
Lyndon.
-----Original Message-----
From: Dave Zug. <dzug at delanet.com>
To: gmecm at diy-efi.org <gmecm at diy-efi.org>
Date: October 5, 2000 2:35 PM
Subject: Re: anti-theft chips ?


>
>----- Original Message -----
>From: Programmer <nwester at eidnet.org>
>To: <gmecm at diy-efi.org>
>Sent: Thursday, October 05, 2000 2:02 PM
>Subject: Re: anti-theft chips ?
>
>
>> I'd think that any type of anti-theft system may be a hodge-podge in an
>> emergency...
>> I'm not much of a software compiler guy, Dave. Been years since I wrote
>> basic <G>...if I wanted to do this in
>> a 7747 bin--how'd I do it ?? I know somebody wrote code to
>> put a speed limiter in a 7747 bin--and it works great. If it's shown
>> to me once...I'm a quick learner. I've seen this before somewhere in my
>> internet travels, but can't remember where. Somebody mentioned a
>> "secret start" sequence -- maybe it was at the GN site, I dunno. I'm not
>> sure
>> if this would work but, how'd you write:
>> 1. If Key on
>
>immediately after the checksum routine place a pointer to a blank location.
>checksum is run at key-on, therefore the patch will run immediately after
>checksum success.
>
>> 2. If TPS + 70% or A/C signal high, or .... PRNDL in R_DL once
>
>Compare present TPS reference ram location with a $80 or something. If .GT,
>then set a ram variable (gotta find an unused bit flag) to true. If not,
>False.
>
>When it comes time to lookup the, say, RPM limit, point to a unused prom
>location insted of the standard prom location and set it to 1 (25 rpm?) IF
>the contents of the flag you set earlier shows improper TPS at key-on.
>
>> 3. Then fuel on ??
>
>I wouldnt mess with fueling - of coarse on a bench it won't be dangerous.
>
>> Will the PCM see this as a one time event at start up--it should I guess?
>> If you don't have time help--no problem...I'll try to figure something
>out.
>>
>
>I'll try to dig up the code sections. There are 3 areas: JSR after
checksum,
>subroutine to compare TPS and set flag, and decision to set the spark table
>pointer, whick uses another subroutine.  In order to do this WITHOUT
>recompiling, the areas in the assembly code that must have JSR's inserted
>have to REPLACE a certain amount of code, therefore the FIRST thing to do
in
>the subroutine is to complete the code that you wiped out for the JSR
>instruction.
>
>Again - ON A TEST BENCH!
>
>> Lyndon.
>>
>> -----Original Message-----
>> From: Dave Zug. <dzug at delanet.com>
>> To: gmecm at diy-efi.org <gmecm at diy-efi.org>
>> Date: October 5, 2000 7:58 AM
>> Subject: Re: anti-theft chips ?
>>
>>
>> >in '97 or so, I patched in code (manually - no compiler) after the
>checksum
>> >to check TPS and compare it with 50%. checksum occurs at key-on and not
>> >otherwise (from what I could find - no other calls to the start of the
>> code)
>> >based on the comparison I would select 1 of 2 spark tables when it came
>> time
>> >to do the 3d lookup. I suppose if you either put the execution into an
>> >endless loop if TPS is not above 50% when the key is turned on.
>Interrupts
>> >may override this though. I made a lengthy post regarding exactly what I
>> did
>> >maybe a year ago. another consideration is liability of coarse.  If the
>car
>> >must be started in a panic, or BORROWED in an emergency it could gum
>things
>> >up. If an accident occurs it will take high paid experts to testify that
>> >there is no way your patch was responsible.
>> >
>> >DISCLAIMER - DO THIS ONLY ON A TEST BENCH, for fun  ;-)
>> >
>> >EFI performance made a security version for their GN chips that required
>a
>> >sequence of activities, something like key, neutral, park, TPS, crank.
>> >
>> >
>> >
>> >----- Original Message -----
>> >From: Programmer <nwester at eidnet.org>
>> >To: <gmecm at diy-efi.org>
>> >Sent: Thursday, October 05, 2000 2:35 AM
>> >Subject: anti-theft chips ?
>> >
>> >
>> >> Anyone ever figure how to write a secret start sequence so
>> >> one wouldn't have to shell out big bucks for an anti-theft
>> >> system that is so easily bypassed ? My secretarys' husband
>> >> had their 89 C1500 SWB stolen right from in front of their house.
>> >> They heard the truck start up and drive away--thought it was a
>> >> neighbor <g>. That was last week--got the truck back today,
>> >> luckily--the idiot that stole it was caught driving drunk...otherwise
>> >> they probably wouldn't have had any action on it at all...
>> >> Lyndon.
>> >>
>>
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>> >>
>> >
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