Heated O2 conversion

[SKFengineer]

1993 GMC C1500, engine is miles from stock as I have installed a BluePrint Engines crate motor that makes about 405 hp with a modified TBI fuel injection setup and headers. I have a tune which is working well but it's a little rough until the one-wire 02 sensor is warmed up on cold mornings. It's perfect from the start during the warmer months. I still slowly play with the tune but in the interest of continuous improvement I'm adding a heated O2 sensor.

So my question, I need to use a 12 positive source that comes on with with the key switch to power the heating feature. I'm trying to figure out if anyone knows how many amps a heated O2 sensor may draw. I was hoping to tap the circuit block on the firewall that powers the fuel pump but I don't want to overload the circuit killing the "critical" fuel pump.

Does anyone have experience tapping into positive keyed sources for this application.

Thanks

[brian617]

On the 94 model which uses same PCM, It's powered by the 10 amp ECM fuse which also powers EGR solenoid, purge solenoid and TCC brake switch.

[SKFengineer]

Thanks, that is a help. I'm going over wiring diagrams to see what is on the fuel pump circuit and if it's just the pump I may use that source.

[brian617]

The fuel pump circuit will only be hot for a short period of time when key first turned on, and then when the engine is running usually redundantly through the oil pressure gauge.

The diagram for showed the heater circuit to be on, key on and start positions. I like the o2 wired key on so you can leave the key on to let the sensor heat up before you start it for a rough idea of start up fuel. I realize its no wide band, but its useful info that can be used with any aftermarket scan tool.

[SKFengineer]

You raise a really good point about getting that active data as soon as you start... That is something i've been trying to get.