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O2 Heater Circuit?


Rearanger

Well-Known Member
Joined
Feb 4, 2008
Messages
1,429
City
Southeast USA
Vehicle Year
2003
Transmission
Manual
As below: 2003 3.0L

Need to know if the heater circuit (keyed on) stays on after engine gets warm or does the PCM turn off the heater.

I have used the fuse for this circuit and an Add-a-Circuit tap to power my electric fan.

Thanks.
 
I think it is just key on power, so shutdown after so long.
 
Further thought on this is the power at the fuse is always on and switched through key then, if switched through PCM if not on after engine gets hot.

I had a couple blips on the speedo needle when the fan turned on and then off. Going to monitor it further. The wire to the fan controller sees few amps, but either way the draw would be through the fuse box supply, before the heater circuit.
 
I pulled my FSM and in the heated O2 sensor description it states the heater is turned on/off as conditions require. It also states that the heater always has power but that the PCM grounds the heater to complete the circuit and activate the heat cycle.

That means the fuse is always hot when the key is on (start/run), which is what I figured out originally using my test light. The PCM heater cycling should have no effect on my fan controller as it draws almost nothing.
 

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