Need a little help.

[fastjohn]

Does anyone have the schematic for the pass key decoder module for a 91' Firebird? I need to know what kind of signal is sent to the ECM for fuel enable. Pin(F10) dark blue wire. By accident, my racing buddy, decided to cut it out, so now I have to bypass this box. Already got the starter enable to work, but engine will not fire. Was running fine before the incident. I do have spark, and fuel to the injectors.

[bsim]

I know I'm missing the details, but I believe it's a resistor value, based upon the PASS key of the car. I think it could be one of 30 values if memory serves right (I doubt it).

[Ed Hamilton]

My son has alldata at work and he came up with this. Let me know if you need anything else.

Ed

 

CIRCUIT OPERATION

 

The brain of the PASSkey® system is a special decoder module that reads the pellet resistance through the lock cylinder contacts. It then compares this key code with its own internal code.

 

If the codes match, the decoder supplies a ground for the starter enable relay and modulates a 5 volt reference signal (at 2.5 volts) from the ECM or PCM which will then pulse the fuel injectors.

 

If the codes do not match, the decoder module sets its internal timer which locks out starter operation and fuel enable for up to three minutes.

[jeffburch]

Measure the resistance of the pellet in the key used.

Replace it with a same value resistor in the circuit.

I have a schematic, but, just follow the two little wires going up to the ignition key. Add it there.

 

Lemme know if ya need some pin numbers.

 

jb

[cmc38camaro]

John,

 

I built VATS bypass in the past and I believe it ended up in Ed Varon's possession. All the thing does is send a series of 30Hz pulses to the ecm at start up. If the ecm sees the pulses it turns on the injector driver circuit. Here's a websitie to get you started:

 

http://www.lt1swap.com/vats.htm

 

Mike

[fastjohn]

Thanks you. The book I have said the signal to the ECM was 2.5 volts, the book never mentioned that the signal was at thirty hertz.

[cmc38camaro]

John,

 

The pulses is more accurately a square wave so it would measure 2.5v on a DVM in the DC range.

 

Mike