SC- 1st Gen (1992-2000)

SC400 Code 25 OBD I

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Old 08-17-14, 11:33 AM
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STORMINORM
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Lightbulb SC400 Code 25 OBD I

FYI: I, too, have experienced a Code 25 on my '93 SC400. In the OBD I system this code, Air/Fuel mixture LEAN, can differ from the specific OBD I codes for O2 sensor failures, i.e., showing codes 21, 27, 28 & 29.

After re-confirming the Code 25, my mechanic hooked up his SnapOn diagnostic reader which showed, in real time, that the front (MAIN) left O2 sensor was constantly reading LEAN while the other three were going from -0- to LEAN to RICH back to LEAN, etc. as we varied the rpm's off idle. We replaced both fronts as the car was already up in the air. Held off on the rears because you have to pull front carpets to unhook them from the wiring harness?

In a nutshell, it was an ABERRANT reading from the one sensor that caused the Code 25. Hope this may help another owner.

Cheers!

p.s. Bought all four specific O2 sensors for about $42.00 each, delivered. While the Stealership wanted to charge me an hour @ $120 for "diagnosis", $235 EACH for the O2 sensors, and who knows how many hours @ $120 to R&R I have a spare(albeit, used) front, both rears NIB in my Lexus parts box...
Old 08-17-14, 12:19 PM
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OG Dada
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No need to pull the carpet off for the rear O2 sensors. Just remove the entire stereo and A/C unit, along with the center bezel and the center trim. From there, you can access the plug for the O2 sensors. Now, before pulling it out from under the car, tie a wire or something strong enough to pull the plug of the new O2 sensor back in after you pull the old one out. Voila, easy peasy lemon squeezy.
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