any one have a lead where i can find the wiring diagram for the ecu and wiring harness for a 99 with anti-theift i belive i can elimnate the anti-theift junk if i just knew which wires was what and what not ive looked up in other threads but the links are not linkable any help pls...

 

I dont have a 99 FSM, but its my understanding that the ECU gets a coded signal from the transponder, rather than a set voltage. un plugging something or bypassing with a resistor or anything of the like will not work.
If someone could identify the transistor inside the ECU, I believe we could jump the NATS transistor inside the ECU. This is just speculation of course.

 

Pg. 297

http://www.nicoclub.com/FSM/maxima/1999/EL.pdf

 

The first thing I would check would be pin 17 of the ECU (or ECM as the FSM labels it). See the bottom of page 297. The NATS immobilizer unit is going to either ground or place 12 volts on pin 17.

It looks like all you need to do is connect pin 17 to a either a 12 volt pull up resistor or pull down resistor to by-pass NATS. This also seems too simple.

 

What do you mean by a 'pull up or pull down' resistor? Never heard a resistor referred to as that. I don't think it will be that simple to be honest. It's not like GM where you can find the value of the resistor in the key / transponder and then just jump the key sense leads .... not to mention, GM has like 20 diff resistor values they use, no telling what Nissan uses. Only thing I can think that may work for you OP is to use a remote start bypass module. Just don't use the rest of the remote start (unless you want to) but the bypass module will fool the NATS into thinking everything is fine. Should anyway ... don't see why this wouldn't work.

Nissan uses an RF signal sent to the BCM to control the NVIS (vehicle imobl sys). Here's a little more info that I found ... Hope this might help, or at least shed some light on the situation.

http://forums.maxima.org/5th-generat...s-problem.html

 

A pull up resistor is a resistor that is used between the power source (12 volts) and the item (the ECU in this case) the power is attached to. The resistor provides current limiting. A pull down resistor is between ground and the item. To connect directly to 12 volts could possibility have bad effects. It depends on the circuitry.

Measure the voltage on pin 17 of the ECU when you have a registered key in the ignition switch and the ignition switch is turned on. Whatever voltage you read is what you want to have on pin 17 to do the bypass.

I don't know anything about whether Nissan uses resistors in the keys. A pull up resistor on pin 17 of the ECU would have nothing to do with what ever is in the key. Pin 17 looks to be the result of NATS sensing/not sensing a registered key. I am somewhat doubtful if this one pin on the ECU is all that is needed to override NATS, but it is at least a starting point.

 

Thank you for the explanation. I agree, it's doubtful it will work sending 'X' Vdc to pin 17, but it's worth a try I guess. I just know that Nissan uses an RF signal to send that voltage, so there has to be a receiver that converts that RF to analog voltage. Our cars don't use resistors in the keys like GM, that was just an example. With it being an RF system, there has to be a passive RF device in the key. Similar to the newer Altima with push to start - no key. It senses the RF signal form the 'key' and acts on a proximity effect. Same principle as the NVIS, just more advanced.

 

I know that there is a RF chip in the key, I have swapped it when I break a key. But the RF thing is just between the key and the receiver that is by/behind the ignition key. I'm hoping the the signal to pin 17 of the ECU is just a voltage level. If its a digital data signal like the windows, a bypass would be pretty costly to make. I don't have an oscilloscope any more to be able to check this.

 

I wonder if there's a way to 'bypass' the NVIS via the BCM ???? Since it is really what tells the ECU what's what. ?????