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Old 01-27-2010, 06:42 PM
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O2 sensor heat question

I am going to instal a TBI fuel injection on my inline 6 250ci Chevy engine. I have read several times that an O2 sensor with a heater is better because it starts working faster.
If I use a heated O2 sensor, is it heated all the time the engine runs, or does it cycle? If it is not heated all the time, how does it work to turn it on and off?
How much current does it use? I need to know where to wire it, relay or not...
Or should I just go for the simpler 1-wire sensor?
I will be using aftermarket cast-iron headers.
Thanks!

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Old 01-27-2010, 07:43 PM
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Three wire heated O2 sensor, 12-volts supplied to it while the ignition is on (all the time), not sure of the fuse rating but I cannot recall a relay being used so it would be likely 10 amps or so, maybe less.
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Old 01-27-2010, 07:48 PM
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IMO, I would go with the heated seeing as you are in Canada. The heated o2 basiclly takes anywhere from 20 to 60 seconds to heat up rather that the 5 to 10 minute warm up time. This will cause your pcm to go into closed loop much quicker, resulting in better fuel economy and cold weather drivabillity. The sensor heater circuit is controlled by the pcm, and is switched on and off as the o2s output voltage changes due to temp. If you do a lot of stop and go driving, the heated o2 will save you fuel due to the fact that the exhaust temps may drop while idling. Rather than go back to closed loop, it will just heat the o2 back up. I believe that the the heated o2s draw about 15 to 20 amps. Hope this helps!
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Old 01-27-2010, 08:49 PM
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IIRC the resistance of the heater is around 5 ohms, so it each heated O2 should pull around 3 amps each. 14.5 volts divided by 5 ohms = 2.9 amps.
a 10~15 amp fuse should be fine.
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Old 01-27-2010, 10:05 PM
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Thanks for these great answers!
Randy_ho, I was wondering about the cycling of the sensor because the TBI pcm I have does not have this function, it comes from a vehicle which had a 1-wire sensor.
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Old 01-28-2010, 12:20 PM
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do you know what year/model car it came from? Some PCM/ECUs did have the functionallity for the 4 wire, just no connection. You may be able to still use it. I have seen some posts on other forums that others are able to convert from 1 wire to four just by making simple connections. Sounds like you may be able to just connect to one of the pins in the PCM connector and tap into the green signal line from the TPS.

Last edited by randy_ho; 01-28-2010 at 12:37 PM.
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Old 01-29-2010, 07:47 PM
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PCM comes from an '89 Chevy Half-ton. That truck had a 1-wire O2 sensor. As far as know, heated sensors were used only on later vehicles with multipoint fuel injection, not on vehicles with TBI. These vehicle would have a different PCM.
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Old 01-29-2010, 08:20 PM
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heated o2 sensor

Hey Wave, goggle converting to heated o2 sensor and you'll get 32,300 hits. The first few have wiring diagrams and all the info you need. olnolan
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Old 01-29-2010, 10:04 PM
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wave has a good point there i cant recall ever seeing anything except non heated on TBI engines.

and on some MPI engines instead of one heated sensor(multi wires) there are 2 or 3 non heated(single wire)ones,

such as on the 2004 chevy trucks 5.3 and the ford taurus 3.0 1990s

and so on..

GM 3800 engines and late model chrysler 4 cyl engines often have the heated sensors

we work on these all the time, so commonly, im just trying to help somehow, lol.
good luck


hmm my name is randy and i am in IL.
my dad is also the same name and in this state somewhere.. hmm.. interesting.... lol. maybe i know you? possibly?
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Old 02-01-2010, 11:20 AM
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Ok, I think in my opinion, I would go with a 3 wire. Easiest method - 1 wire to the sensing line, 1 to ground, and one to switched power. This will work, just keeping your o2 heated all of the time.
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