First of all where can I get one and is there a specific brand or part number that I want? Also there has to be some modification to the stock wiring connector right? I mean the heated o2 sensor has 3 wires and the stock one has 1 right?

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Riccioli Performance Motorworks

--RPM Racing--

Getting there.....383 with Super Ram, Bosch 24# SVO's, MSD, Edelbrock 58 mm TB, 700R4 tranny, Eibach springs, Koni 12 way adjustable shocks and struts, and more!! Now let's pray it runs when it's all back together!!!!

 

Paul,

The three-wire HO2S are easy to wire into the existing circuit. They were available in 1992 and 1993 LT1s. I think the GM part number for the 3-wire HO2S is 25162693, and it lists for $52.81 each. You should use a relay to isolate the heater elements from the ECM directly:



If you decide to use the later model four-wire sensor, they are similar:




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Later,
Vader
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Justice and Freedom will Prevail

[This message has been edited by Vader (edited September 23, 2001).]

 

Vader, I believe you need to switch your NO and NC connection to the HO2S.

If the sensor is wired to the NC terminal on the relay and you energize the relay, the common then goes to the NO.

 

Mike,

You are correct - The N.O. will be closed when the relay is energized.

However, the relay is only energized when the EVAP purge solenoid is powered. That means the coolant will be above 158°F and the ECM will be in closed-loop mode. When in closed-loop, the heaters do not need to operate. Exhaust gas temperature is usually adequate to maintain effective sensor temperature. If the EGT drops low enough to affect the sensor(s), the ECM will drop from closed-loop, and the EVAP will again disable, turning on the O2 sensor heaters again until they are warm enough. The default position is ON, so the heaters are energized right from the start, but cycled off when not needed.

The OEM installations of HO2S in GM cars use modulated heat similar to this. We might as well do it on our cars as well. The one advantage of the newer PCMs is that they will duty cycle the heaters to maintain heat rather than turning them off and on in such large steps. In either case, disconnecting the heater(s) when the EGT is high enough will prolong the life of the sensors, and they aren't $22.95 specials at AutoZone - the cheap ones are fifty buck apiece.

But thanks for taking time to look at the circuit.

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Later,
Vader
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Justice and Freedom will Prevail

 

I see, I made a poor assumption that A3 was grounded all the time, didn't even pay attention to the EVAP on the schematic.

I'd wondered about the longevity of the HO2S always being on. I think I asked someone about this before (HO2S being on always) and the response was that it should last as long as scheduled replacement intervals would be.

What's the recommended replacement interval on the newer F-Body cars with the HO2S's?

IIRC, 30K miles is recommended for our cars.