another mystery no start issue
04-06-2018, 08:43 PM
#22
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Join Date: Nov 2006
Location: Goldsboro, NC
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i hear ya about the shotgun. rifle works better actually, better penetration 
i have the service manual for my 2002 and looking at the starting/charging electrical diagram:
ignition key start - fuse block underhood 15A (h10-h11) - branches two ways below
branch A to PCM starter relay coil supply voltage. Connector id C1=80 BLU, C2=80 CLR. It also mentions V6 L36 on this branch so i don't know if that means does not apply to LS1. wire color i think is PPL/WHT = purple white stripe. this branch ends here at PCM.
branch B branches out twice. first is to Instrument Panel cluster (logic) starter relay coil supply voltage, and ends there. The relevant part is to clutch pedal start switch for manual trans or park/neutral switch for automatic and is PPL/WHT wire. After this safety switch, Dark Green wire to fuse block underhood starter relay.
here's where it gets fun.
heavy current side of relay that powers starter, gets power from main bus. output is purple wire to starter solenoid. you are most likely jumping this part of the circuit and engine is starting.
On low current coil side of relay, the input is coming from the neutral safety switch that dark green wire. Output from relay coil side has to go to ground for it to function! And it goes to the body control module, which is described as starter enable relay control and looks like it's a yellow/black wire. The BCM then grounds the circuit provided the VATS system is working or properly disabled, and whatever else.
My best guess is your BCM is preventing the ignition key start from working.
you can bypass it by going under the fuse block under the hood for the starter relay, finding the grounding wire to the starter relay and putting it directly to ground instead of the BCM. I believe this would be a better way to disable VATS rather than ******* around under the steering column with resistors. By running the starter relay coil actually to ground the starter should work, otherwise you have a problem somewhere in the circuit between ignition key and starter relay, or the power feed to the relay is bad.
Whether the PCM talks to the BCM about security and starting I don't know, if it does then it would then prevent the engine from running but you seemed to already prove that this isn't the case. hope this helps.
regarding vats, i'm pretty sure it's only a engine start preventing thing and it looks that way according to the electrical schematics and descriptions.
i have the service manual for my 2002 and looking at the starting/charging electrical diagram:
ignition key start - fuse block underhood 15A (h10-h11) - branches two ways below
branch A to PCM starter relay coil supply voltage. Connector id C1=80 BLU, C2=80 CLR. It also mentions V6 L36 on this branch so i don't know if that means does not apply to LS1. wire color i think is PPL/WHT = purple white stripe. this branch ends here at PCM.
branch B branches out twice. first is to Instrument Panel cluster (logic) starter relay coil supply voltage, and ends there. The relevant part is to clutch pedal start switch for manual trans or park/neutral switch for automatic and is PPL/WHT wire. After this safety switch, Dark Green wire to fuse block underhood starter relay.
here's where it gets fun.
heavy current side of relay that powers starter, gets power from main bus. output is purple wire to starter solenoid. you are most likely jumping this part of the circuit and engine is starting.
On low current coil side of relay, the input is coming from the neutral safety switch that dark green wire. Output from relay coil side has to go to ground for it to function! And it goes to the body control module, which is described as starter enable relay control and looks like it's a yellow/black wire. The BCM then grounds the circuit provided the VATS system is working or properly disabled, and whatever else.
My best guess is your BCM is preventing the ignition key start from working.
you can bypass it by going under the fuse block under the hood for the starter relay, finding the grounding wire to the starter relay and putting it directly to ground instead of the BCM. I believe this would be a better way to disable VATS rather than ******* around under the steering column with resistors. By running the starter relay coil actually to ground the starter should work, otherwise you have a problem somewhere in the circuit between ignition key and starter relay, or the power feed to the relay is bad.
Whether the PCM talks to the BCM about security and starting I don't know, if it does then it would then prevent the engine from running but you seemed to already prove that this isn't the case. hope this helps.
regarding vats, i'm pretty sure it's only a engine start preventing thing and it looks that way according to the electrical schematics and descriptions.
04-09-2018, 10:54 AM
#23
There are some misconceptions and assumptions in this thread that are not entirely accurate. VATS (Vehicle Anti Theft System) prevents theft by controlling two separate functions. If it does not detect the correct resistance in the key pellet when starting, it will disable the fuel enable signal to the PCM and it will remove the ground to the coil (low voltage) side of the starter relay. The BCM (which contains the VATS circuitry) cannot be programmed so despite the claims of some tuners, you can't "program out" VATS. You can program the PCM to ignore the lack of a fuel enable signal but you can't program the starter relay ground. This is what seems to have happened to the OP - he assumed it couldn't be VATS because it had been "programmed out" but that only handled the fuel not the starter.
There are two ways to get around VATS... you can do the traditional bypass with resistors which makes the system see the correct resistance all the time regardless of the key pellet; or you can program the PCM to ignore the lack of fuel enable signal AND provide a separate ground for the starter relay coil (either one by itself is not sufficient).
To provide the separate ground for the starter relay, find the relay in junction box #2 under the hood on the left fender well, look underneath the box and find the yellow/black wire going to the relay, cut the wire with enough slack to work with and then run the relay end of the cut wire to a good chassis ground (you will need additional wire spliced on to reach a good ground). Be sure to tape up the other end of the yellow/black wire that goes into the harness.
There are two ways to get around VATS... you can do the traditional bypass with resistors which makes the system see the correct resistance all the time regardless of the key pellet; or you can program the PCM to ignore the lack of fuel enable signal AND provide a separate ground for the starter relay coil (either one by itself is not sufficient).
To provide the separate ground for the starter relay, find the relay in junction box #2 under the hood on the left fender well, look underneath the box and find the yellow/black wire going to the relay, cut the wire with enough slack to work with and then run the relay end of the cut wire to a good chassis ground (you will need additional wire spliced on to reach a good ground). Be sure to tape up the other end of the yellow/black wire that goes into the harness.
