Check Engine Light-Main oxygen sensor fault

1989 TOYOTA PICKUP
200,000 MILES • 2.4L • 4 CYL • RWD • MANUAL
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THOMASNATALE
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ODB1 error code 21 1. Are there two sensors? 2. How do you determine if it is just needing a new sensor and if there are two which one is the bad one? 3. Can you point me to where a diagram will show the location of the sensor(s)? 4. Are these very difficult to remove and replace?Thank you!
Apr 7, 2015 at 11:43 AM
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HMAC300
  • ✓ASE Certified Mechanic
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there is only one it will be in manifold or exhaust pipe close to engine. they are easy to replace. there is no diagram of these.
Apr 7, 2015 at 12:22 PM
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THOMASNATALE
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Thanks for the answer. Since the engine is still running fine, is it most likely just the sensor is bad? Thanks again.
Apr 7, 2015 at 1:18 PM
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HMAC300
  • ✓ASE Certified Mechanic
  • 48,601 POSTS
  • ASE Certified Mechanic
cold be that but until you actually check it then I can't say. it can also be a short in wiring or maybe a bad pcm. but try a sensor due to it's age.
Apr 7, 2015 at 3:09 PM
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