RENE'S RAGE

iTrader: (96)

I'm in the process of removing all unwanted wires from my car.
It's a race car only.
I have one question now maybe more later on. LOL.
I'm removing the BCM now, I've got the start relay figured out, just ground the yellow/black wire at the relay.
I don't know what to do with the blue wire (fuel enable wire). That goes to the PCM.
What acually does this wire do?
Does it tell the PCM to pull in the fuel pump relay?
Can I just jump the fuel pump relay out, and and bypass this wire?
Thanks George

MikeFbody

iTrader: (2)

you can't just jump that wire anywhere. It does tell the PCM to enable the fuel pump, it's part of VATS, but it does not use a 12v signal (that would make VATS's incredibly easy to bypass if it was). If I remember correctly, it's a 5v signal at a particular frequency. I remember seeing some info about being able to build / buy a circuit that would replicate that signal to the PCM, or, I believe you can have the PCM flashed to not require the fuel enable circuit with a number of the PCM programmers on the market today.

-mike

WhiteBird00

iTrader: (4)

As you know, the BCM disables the car for VATS in two ways. It prevents the starter from operating by removing the ground from the coil side of the starter relay and it prevents the engine from running by not providing a fuel enable signal to the PCM which effectively cuts off the fuel pump.

The starter relay ground is easy to bypass by just providing a normal chassis ground on the circuit as you have done. The schematic for the fuel enable signal shows that it is a ground signal handled within the BCM but I believe Mike is right that it is not a 12V ground. There are no details of the internal workings of the BCM available.

The PCM can be programmed to ignore the fuel enable signal thus bypassing VATS. The tuner lists the option as "disabling VATS". That's why we get so many questions like "I've disabled VATS with a tuner but the car still won't start." They don't realize that the tuner can't eliminate the starter relay problem by itself. But in your case it works to your advantage - you've already bypassed the starter relay so you just have to program out the fuel enable signal in the PCM.

RENE'S RAGE

iTrader: (96)

Can I pull the fuel pump relay in by sending 12v to the coil?
I think the relay has a ground all ready. I think the PCM sends a 12v wire to the relay.
I may be wrong, I'll trace the wires again.

WhiteBird00

iTrader: (4)

The fuel pump relay gets constant power (hot at all times) through the fuel pump mini-fuse in the junction block under the hood. The PCM then turns it on and off in the same way as the BCM controls the starter relay - by controlling the ground to the coil side of the relay. If you were to substitute a chassis ground you would have the fuel pump energized at all times which is probably not desirable.

RENE'S RAGE

iTrader: (96)

I have a wiring diagram from a Haynes Manual, it shows the orange wire from the fuel pump mini fuse to one side of the relay and the other side has a gray wire going to the fuel pump.
The coil shares a ground with the oil level sensor, which is grounded to the chassis.
Then the dk grn/wht to the PCM (Fuel Pump Relay Ctrl).
I've trace these wires again, and that's where they go.
So I'm thinging the dk/wht from the PCM is what pulls the coil in.
So I'm thinking it has to be 12v.
I could pull the coil in with a toggle switch by breaking a 12v source to the relay coil.
Or am I not seeing the whole picture here?
Thanks George

WhiteBird00

iTrader: (4)

Sorry, you're right (I hadn't had my coffee before I posted).

The switched side of the relay gets constant power from the fuel pump min-fuse through the orange wire and goes to the fuel pump through the gray wire. The coil side has a chassis ground at G110 and is powered by the fuel pump relay control circuit of the PCM through the dark green/white wire.

I don't think you'd need a separate switch to control the relay coil. I would think you could tap any circuit that is hot in the on and start positions of the ignition switch.

RENE'S RAGE

iTrader: (96)

Yeah, I'll probally tap on to the ignition circuit.
So if I ground the start relay, and send a 12v hot to the fuel pump relay, can I get rid of the whole BCM. Is there anything else I need to modify to get the car to start and run
correctly.
Thanks for your knowledge and time.
George

WhiteBird00

iTrader: (4)

Aside from VATS, eliminating the BCM will disable power locks, hatch release, power windows, radio, courtesy lamps, keyless entry, alarm (if equipped), audible chimes, and several warning lights such as seat belt and door ajar. The radio and windows are only disabled because they run off the retained accessory power (RAP) circuit which is controlled by the BCM. You could substitute ordinary ignition-switched power to make them work again.

I assume you are doing this for race use and don't plan to use the car on the street?

RENE'S RAGE

iTrader: (96)

Yes race car only, no street. One other question, the white wire @ PCM c2 #10.
My wiring diagram said it's the Engine Speed (Tach) Output Signal.
I traced this back to the ABS. I removed all the ABS wires, will my tach still work or what do I have to do to make it work again.
Thanks

RENE'S RAGE

iTrader: (96)

Anyone on the tach wire?

shoemike

iTrader: (25)

It's not the "tach wire", it is the engine speed signal to the EBCM.

The tachometer in the IPC gets it's signal from the PCM via class 2 serial data.
All the modules (PCM, IPC, EBCM & IRSDM) are connected through a splice pack (star).

So as long as you don't remove the PCM or IPC from the star connector the tach should work.

RENE'S RAGE

iTrader: (96)

What's the IPC and IRSDM?
I know where the star connector is.
Yeah, I didn't think that went to the tach, but I also read somewhere you could use that wire for a shift light or a remote tachometer.
Thanks

shoemike

iTrader: (25)

IPC = Instrument Panel Cluster

IRSDM = Inflatable Restraint Sensing and Diagnostic Module