92 lesabre doesn't crank, power OK

[feniks]

hi people

so ... it seems i shouldn't have messed with this car (a/c system) haha, now it's paying me back...

all was running "great" (as usual) until yesterday when i saw SECURITY indicator light staying on when driving a few times (lots of short trips). however car was starting with a touch of ignition, literally instant engine start.

a lil history:
both alternator and starter were replaced about 4-5 years ago.

serpentine belt, air & fuel filter, spark plugs and spark plug wires are all less than year old and were replaced last fall.

battery is about 2 yrs old.

MAF was cleaned like 2 weeks ago

since today symptoms:
a) power is OK, all lights running strong with key at IGN ON (clock shows correct time).
dash shows same lights as usual (not sure if SECURITY should stay lit up or not though)

b) when trying to crank engine (key at ACC) literally there is no cranking at all. also i noticed that that the moment i turn key to crank engine the BRAKE and INFL REST lights come up and the clock goes off at same time...

so far i only checked IGN 60A fuses in Main Engine Relay box under hood and they are OK. any ideas ?

what happened to it literally over 1 night ?

[feniks]

never mind, i think i found the answer:
http://wiki.answers.com/Q/What_do_yo..._start_the_car

it seems this car has some sort of a cheap immobilizer (somewhat) which locks the starter if ignition key doesn't get recognized (resistance mismatch for anti-theft ECU) ...

will look into that. wondering what triggered the Security light in first place and what's most strange how da hell i was able to start the engine and drive around with Security light on yesterday ... weird ...

just compared my set of buick keys with my wife's (she never uses this car). looks like the resistor in ignition key on my set is worn and almost flat, so it doesn't make contact with 2 magical wires in ignition cylinder which in results locks out the starter circuit (Security light).

UPDATE:
yup, backup set of keys works fine. I measured resistance of my old worn ignition key's resistor in blade and it reads much higher than the one in backup ignition key.

[imidazol97]

Originally Posted by feniks

it seems this car has some sort of a cheap immobilizer (somewhat) which locks the starter if ignition key doesn't get recognized (resistance mismatch for anti-theft ECU) ...

yup, backup set of keys works fine. I measured resistance of my old worn ignition key's resistor in blade and it reads much higher than the one in backup ignition key.

I wouldn't think that wear on the metal contact sticking out of the resistor portion of the key would cause a change in resistance that is meaningful. Are the contacts dirty or coated with something that's changing the resistance? Rub them with a pencil eraser; the eraser contains a little grit that helps clean.

If they are physically worn down, the two metal contacts inside the ignition lock where the key inserts may not touch them hard enough to get a proper reading of the resistance.

Originally Posted by feniks

UPDATE:
yup, backup set of keys works fine. I measured resistance of my old worn ignition key's resistor in blade and it reads much higher than the one in backup ignition key.

Get a new key cut to replace the one you're using.

The theft deterrent stops the starter from being able to engage and it also stops the fuel injectors. There are 15 different resistances for the keys, so a thief couldn't test them all because of the 3 minute wait after trying the wrong resistance 3 times. Kind of slows down peeling the steering column to force the igntion switch and inserting a resistor to fool the CPU.

If the resistance changes after starting, the light may go on and off but the computer does not turn off the car. That explains why you were able to keep driving.

Good luck with the new keys. And there is a bypass where a resistor is inserted to replace the wires up the column to the key so that the computer always reads the correct resistance.

[feniks]

yup, got it all covered as described before. thanks for a reply though

ignition cylinder is fine as it starts right up with a backup ign key (no Security light with this one).

i measure resistances of both keys and my old worn one reads 200ohm higher than the working one. ordered a blank key with correct resistance off ebay, will bring it for cutting in Home Depot once i get it as they do not carry such blanks anymore.