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How To Check GM 1995 Anti-Theft Relay and Module?

(1995 Chevrolet Lumina)
in Moorpark, CA on August 28, 2013
I suspect that my Lumina-sedan 3.1L 95's anti-theft relay is malfunctional, and giving me troubles starting the engine, such as low or no voltage on the starter's solenoid terminal (S). How to check it remotely? Since it is buried below the passenger-side dash board, it is quite diffcult to access. If I use a wire jumper to bypass the relay, will that cause other problems, electrically, long-run?
Displaying 2 answers & 4 comments
Popular Answer
on September 06, 2013
Don't try to bypass it. Not a good idea. You need to clarify something for me though. When the car won't start, does it crank over normally? If you have a No Crank condition, you need to check the basics first. Battery, Voltage drop the battery cables, Ignition switch Signal to starter, Starter Relay, and Starter. If you have good signal on the purple wire to the starter everytime you hit the key but it won't crank, you need a starter. If you have no signal at all, it could be an anti-theft problem (is the security or other theft indicator light on or flashing when it won't start?) or even the transmission range switch, but most likely it is either the Starter relay, ignition switch or possible high resistance or a break in the wire. Try using a DVOM instead of a testlight. If you get voltage (greater than .5 V) on the purple wire at all, it is not the transmission range switch or anti-theft system. You can eliminate one test quickly. Remove the starter relay and replace it with another relay from the electrical box that has the same number on top of it and is in a system that you know works. If it still does the same thing, it is not the relay. Let me know the results of the tests I've given here.
on September 11, 2013
Thank ChevyASE! It turned out to be the starter relay going bad, coupled with the intermitten-high resistance problem of the neutral safety switch, which is also housed with the transmission range switch. I use a wire jumper to bypass the neutral safety switch; I only start the engine in the park position. Now the engine starts fine. However, I wonder if this could cause any problems with the transmission range switch; I did not touch any wires for the transmission range switch!

Also, for the anti-theft relay, does it sometimes break down? My car has about 190K miles. Thank!
on September 13, 2013
Replace the transmission range switch. They are not expensive or hard to do. Just make sure you set it right so it only starts in P or N and the dash or console indicator (PRNDL) reads right and reverse lights work correctly. I have seen VERY FEW theft relays and even FEWER theft modules go bad. Usually a theft system problem (especially on the Pass Key 1 and 2 systems) is caused by the chip on the key getting worn, and/or the wire(s) to the Ignition Lock Cylinder breaking.
on September 13, 2013
Thank ChevyASE for your reply. Lastly, I now see another smaller also-called neutral safety switch, locating just above-near the steering wheel column. The switch only has two wires and a push-pull enable pin. May I ask what is this switch for? how does it work with the transmission P/N switch? thanks!
on August 15, 2014
the car is in sercurity mode when i bypass the purple wire to the starter it starts for one second with the switch in the on position and shuts the engine off
on December 07, 2016
You have to do a relearn
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