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93 Sc400

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How many O2 sensors are on a 93 SC400?

I keep getting Err 27, but it doesn't tell me which O2 sensor is giving the problem. Is it better to replace with an OEM sensor or an after-market? Auto Zone sells a universal O2 sensor, is this adequate?

I've also heard references to wide-band O2 sensors, is this something I should consider?

Each OEM sensor is $121.39, is this a good price?

If I replace one, should I replace all?

It seems there are (3) sensors, one front and a rear left and a rear right!

Thanks for your help!


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DTC #27

(1) Open or short in heater circuit of sub heated oxygen sensor for .5sec or more.

  • Open or short in heater of sub heated oxygen sensor
  • Sub heated oxygen sensor
  • ECM

(2) Main heated oxygen sensor signal is .45v or more and sub heated oxygen sensor signal is .45v or less under the following conditions:

(two trip detection logic)

  • Engine coolant temp. : 80*C (176*F) or more
  • Accel pedal fully depressed for 2sec. or more
  • Look up same list

I'd replace all sensors. The universal should be fine but you should check to be sure. Just pull the old one off and get a number or compare the leads to the universal. Make sure they wire up the same. NGK makes some of the most reliable sensors is what I've read.

Looks like you've got two sub's - right and left just behind the catalytic converters. They plug in through the floor boards. You have two mains as well. Right and left. They should be in the exahuast manifold area most likely under a heat shield or something. Can't quite tell by this picture. Just look around tracing the exhaust off the head and you'll find them.

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You can get wideband O2 sensors, but they wont be very useful in your application. The W/B sensors will run around 0-5v while the Toyota oscillates between 0-1v i believe. You can get the W/B for as cheap as $28 or over $200 but the factory ECU wont read the signal since its looking for an oscillation betwen 0-1v. You can get a WideBand controller like the Innovative Motorsports LM-1 which alot of people use around here, but only for performance purposes. Unless youre changing your fuel curves or going forced induction, the stock O2 sensors should work fine

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