Antitheft system problems.

[crimsonride]

I'm swaping a 3.4 into my cherokee. I can get it to fire up but it kills imediately. I'm thinking this is the antitheft system shutting down the fuel injectors. I can get the engine to run and stay running if I brush the antitheft wire from my harness on a grounded surface, if it's solidly grounded it won't stay runing and if it's not grounded at all it won't stay running.
Also, when it is running, it runs rough as if it's not on all cylendars.

Does anyone know what I'm supposed to do with this? Am I missing something I need?

[CNCguy]

Re: Antitheft system problems.

I'm swaping a 3.4 into my cherokee. I can get it to fire up but it kills imediately. I'm thinking this is the antitheft system shutting down the fuel injectors. I can get the engine to run and stay running if I brush the antitheft wire from my harness on a grounded surface, if it's solidly grounded it won't stay runing and if it's not grounded at all it won't stay running.
Also, when it is running, it runs rough as if it's not on all cylendars.

Does anyone know what I'm supposed to do with this? Am I missing something I need?

If the donor car had the VATS on it, you will need to disable it. It can be done either by reprogramming the ECM or by making/buying a VATS by-pass unit. I did the latter on my swap.

With my by-pass removed, the motor fires and runs until you release the key from start position. It dies as soon as you release the key.

This link has some info on making one.

http://home.hiwaay.net/~davida1/passkey.htm

Or you can get one on Ebay

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33720&item=2460507078

Marc

[bbeck]

digging up an old thread here.. but, how much do all the components run to build this module?

[robertisaar]

not much... all you need is a resistor value that matches the key. could use a potentiometer and literally tune it into the right range, but if it's close enough to a normal resistor value, i would go that way.

[bbeck]

I already have a resistor in place of the pellet before the steering column. However, the injectors won't fire. I believed this box to replace the signal generator for that part of the system- not the cranking part. By the way, the resistors were like a couple bucks.

[bbeck]

I guess my options are:

- replace the passkey box with another (too expensive and likely to break again)

- replace the passkey box with a simulator/signal generator (about 20 bux on ebay)

- tune it out in a chip for the pcm to stop looking for a signal from the bcm to fire the injectors (the way i'd like to go, but don't have tuning equipment yet)

[robertisaar]

going by that diagram that was posted, likely less than $10... and that's with radioshack prices too...

[bbeck]

thanks, I'm not familiar with all the parts in the list and their prices. I might swing by a radioshack tomorrow and see if they have everything.

[robertisaar]

i was just at my local one a month ago and the only thing i think they might not have is the 555... maybe the zener diode too, but most of it is fairly common stuff.

[Jeremy90]

in my 97 lumina i was having that problem it would start then die after replacing everything electrical or that i could think of thank god my dad knows a friend that works at gm otherwise the pcm would be massively expensive and pretty much it came down to finding a small box i believe was the vats we unplugged it left it unplugged ran no problem wont start by the key had to make a switch to start it going from the battery to the starter with the switch coming out under the dash but hey it runs quite well but now i have to be careful over 70 mph that speedo flies up and before i know it im doing 90 and i wonder why everyone is going so slow lol but yea pretty much just remove the box and the relay in there (200$ part) and try it then itll be a small box screwed onto a plate with a relay next to it and bam could work